Year 5: Rounding decimals
Part of the Year 5 decimals and percentages chapter. Chapter overview · whole chapter on one page
Rounding decimals
To round a number, find the two numbers it lies between, then decide which one it is closer to. Look at one digit: the digit just after the place you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
The number line shows 3.67. It is between 3.6 and 3.7. The halfway point is 3.65, and 3.67 is above it, so 3.67 rounds up to 3.7 to one decimal place.
Key ideas
- To the nearest whole number, look at the tenths digit: 5 or more rounds up (4.5 rounds up to 5).
- To one decimal place, look at the hundredths digit: 5 or more rounds the tenths up.
- Rounding 2 decimal places to 1 decimal place: 6.25 rounds to 6.3 and 6.24 rounds to 6.2.
- Money is rounded in the same way: £7.65 is about £8 to the nearest pound.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.4.36 is between 4 and 5
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 4.5
- Look at the digit after the place you are rounding to. The digit is 3. 4 or less: round down.4.36 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.4
Check. The difference is 0.36, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.7.85 is between 7.8 and 7.9
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 7.85
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.7.85 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.7.9
Check. The difference is 0.05, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.12.48 is between 12 and 13
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 12.5
- Look at the digit after the place you are rounding to. The digit is 4. 4 or less: round down.12.48 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.£12
Check. The difference is 0.48, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Watch out
Round only once. The number 3.449 rounds to 3.4 to one decimal place: the hundredths digit is 4, so round down. Do not round to 3.45 first and then to 3.5.Exercise 7C Rounding decimals
Non-calculatorKey words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.3.27 is between 3 and 4
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 3.5
- Look at the digit after the place you are rounding to. The digit is 2. 4 or less: round down.3.27 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.3
Check. The difference is 0.27, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.5.86 is between 5 and 6
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 5.5
- Look at the digit after the place you are rounding to. The digit is 8. 5 or more: round up.5.86 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.6
Check. The difference is 0.14, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.7.5 is between 7 and 8
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 7.5
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.7.5 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.8
Check. The difference is 0.5, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.9.49 is between 9 and 10
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 9.5
- Look at the digit after the place you are rounding to. The digit is 4. 4 or less: round down.9.49 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.9
Check. The difference is 0.49, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.4.82 is between 4.8 and 4.9
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 4.85
- Look at the digit after the place you are rounding to. The digit is 2. 4 or less: round down.4.82 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.4.8
Check. The difference is 0.02, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.0.37 is between 0.3 and 0.4
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 0.35
- Look at the digit after the place you are rounding to. The digit is 7. 5 or more: round up.0.37 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.0.4
Check. The difference is 0.03, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.6.05 is between 6.0 and 6.1
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 6.05
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.6.05 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.6.1
Check. The difference is 0.05, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.2.96 is between 2.9 and 3.0
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 2.95
- Look at the digit after the place you are rounding to. The digit is 6. 5 or more: round up.2.96 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.3.0
Check. The difference is 0.04, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.7.65 is between 7 and 8
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 7.5
- Look at the digit after the place you are rounding to. The digit is 6. 5 or more: round up.7.65 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.£8
Check. The difference is 0.35, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.12.49 is between 12 and 13
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 12.5
- Look at the digit after the place you are rounding to. The digit is 4. 4 or less: round down.12.49 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.£12
Check. The difference is 0.49, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.0.95 is between 0 and 1
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 0.5
- Look at the digit after the place you are rounding to. The digit is 9. 5 or more: round up.0.95 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.£1
Check. The difference is 0.05, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.3.5 is between 3 and 4
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 3.5
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.3.5 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.£4
Check. The difference is 0.5, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.8.09 is between 8 and 9
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 8.5
- Look at the digit after the place you are rounding to. The digit is 0. 4 or less: round down.8.09 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.8
Check. The difference is 0.09, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.15.5 is between 15 and 16
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 15.5
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.15.5 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.16
Check. The difference is 0.5, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.2.71 is between 2 and 3
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 2.5
- Look at the digit after the place you are rounding to. The digit is 7. 5 or more: round up.2.71 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.3
Check. The difference is 0.29, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.20.44 is between 20 and 21
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 20.5
- Look at the digit after the place you are rounding to. The digit is 4. 4 or less: round down.20.44 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.20
Check. The difference is 0.44, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Round each number to the nearest whole number, then check which ones give 5.
- Round each number. Look at the tenths digit. 5 or more rounds up.
Number Rounded Gives 5? 4.6 5 yes 5.49 5 yes 5.5 6 no 4.49 4 no - Write the numbers that round to 5. Only these two give 5.4.6 and 5.49
Check. 4.6 rounds to 5, and 5.49 rounds to 5. 5.5 rounds up to 6, so it is not included. ✓
Watch out. 5.5 rounds UP to 6, but 4.49 rounds DOWN to 4.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.3.67 is between 3.6 and 3.7
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 3.65
- Look at the digit after the place you are rounding to. The digit is 7. 5 or more: round up.3.67 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.3.7
Check. The difference is 0.03, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.2.75 is between 2 and 3
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 2.5
- Look at the digit after the place you are rounding to. The digit is 7. 5 or more: round up.2.75 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.3 litres
Check. The difference is 0.25, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.2.75 is between 2.7 and 2.8
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 2.75
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.2.75 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.2.8 litres
Check. The difference is 0.05, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.1.36 is between 1.3 and 1.4
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 1.35
- Look at the digit after the place you are rounding to. The digit is 6. 5 or more: round up.1.36 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.1.4 m
Check. The difference is 0.04, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.6.84 is between 6 and 7
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 6.5
- Look at the digit after the place you are rounding to. The digit is 8. 5 or more: round up.6.84 is above halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.7 km
Check. The difference is 0.16, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to the nearest whole number. These are the two numbers it could round to.14.36 is between 14 and 15
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 14.5
- Look at the digit after the place you are rounding to. The digit is 3. 4 or less: round down.14.36 is below halfway, so round down.
- Write the answer. Keep the place you rounded to, and drop the digits after it.14 cm
Check. The difference is 0.36, which is at most half a step (0.5). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the mistake by working out the correct answer yourself, then compare.
- Work out the correct answer. Do the calculation one step at a time.3.449: the tenths digit is 4, and the next digit (the hundredths) is 4. 4 or less, so round down: 3.4.
- Compare with the pupil’s answer. Ella wrote 3.5.She rounded 3.449 to 3.45 first, and then rounded 3.45 up. She should look at only one digit, the hundredths digit (4).
- Write the correct answer. The correct answer is 3.4.
Check. 3.4 is closer to 3.449 than 3.5 is. ✓
Watch out. Round ONCE, using the digit just after the place you are rounding to.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Look at the digit after the units for each number. Then decide whether to round up or down.
- Round 7.49. The tenths digit is 4, which is 4 or less, so round down.7.49 rounds to 7
- Round 7.5. The tenths digit is 5, which is 5 or more, so round up.7.5 rounds to 8
- Explain the difference. The two numbers are very close, but they are on different sides of the halfway point, 7.5.7.49 is below 7.5 and 7.5 is exactly halfway, so 7.5 rounds up.
Check. 7 and 8: the two numbers are on opposite sides of the halfway point. ✓
Watch out. Halfway (7.5) rounds up. Anything just below halfway rounds down.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Find the two numbers it lies between, find the halfway number, then see which one it is nearer to.
- Find the two numbers it is between. We round to one decimal place. These are the two numbers it could round to.2.75 is between 2.7 and 2.8
- Find the halfway number. The halfway number is exactly between the two. A number at or above halfway rounds up.Halfway = 2.75
- Look at the digit after the place you are rounding to. The digit is 5. 5 or more: round up.2.75 is exactly on halfway, so round up.
- Write the answer. Keep the place you rounded to, and drop the digits after it.2.8
Check. The difference is 0.05, which is at most half a step (0.05). ✓
Watch out. Look at ONE digit only. Do not round twice: 3.449 is 3.4 to one decimal place, not 3.5.
Key words. To round a number is to change it to the nearest value in a given place, such as the nearest whole number or one decimal place. The halfway number is exactly between two numbers. A digit of 5 or more rounds up; a digit of 4 or less rounds down.
Method. Try each number with a 9 in the hundredths place. Round each one to one decimal place and see which gives 7.3.
- List the numbers with a 9 in the hundredths. The number is 7 and something, then the hundredths digit is 9.7.09, 7.19, 7.29, 7.39, 7.49, 7.59, 7.69, 7.79, 7.89, 7.99
- Round each one to one decimal place. Look at the hundredths digit. A 9 there always makes the tenths go up by one, so the tenths digit must be 2 for the answer to be 7.3.
Number To 1 dp Gives 7.3? 7.09 7.1 no 7.19 7.2 no 7.29 7.3 yes 7.39 7.4 no 7.49 7.5 no 7.59 7.6 no 7.69 7.7 no 7.79 7.8 no 7.89 7.9 no 7.99 8.0 no - Write the answer. Only one number is left.7.29
Check. 7.29 rounds to 7.3. The numbers 7.19 and 7.39 do not. ✓
Watch out. A 9 in the hundredths place always rounds the tenths UP. Work out which tenths it starts from.