Year 1: One more, one less, counting on and back
Part of the Year 1 numbers to 10 chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
One more, one less, counting on and back
A number line helps us count. Each number is one step further along than the number before it. Start at 0 on the left and count on to the right.
One more is the next number. One less is the number just before it.
Key ideas
- Counting on means moving one step to the right each time.
- Counting back means moving one step to the left.
- One more is the next number.
- One less is the number before.
Key words. One more is the next number. One less is the number just before.
Method. Start at 5. One more is the number after 5.
- Start at 5. Put your finger on the number.Start: 5
- Move one step forward. Each step on the number line is one number.5 + 1 = 6
- Write the answer. 6
Check. Check it: 6 − 1 = 5. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 9. One less is the number before 9.
- Start at 9. Put your finger on the number.Start: 9
- Move one step back. Each step on the number line is one number.9 − 1 = 8
- Write the answer. 8
Check. Check it: 8 + 1 = 9. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Method. Count back from 10 to 7. Each number is one less than the number before it.
- Start at the first number. We start with the biggest number.10
- Take away one each time. Each number is one less than the one before.10, 9, 8, 7
- Write the numbers. Include the start number and the end number.10, 9, 8, 7
Check. Count on from 7 to 10 to check. ✓
Watch out. Count backwards in the same way each time. Do not skip a number.
Watch out
Watch out: “one more” means the next number, not the one you start from. One more than 6 is 7, not 6.
Exam tip
Grown-up tip. Use a number line drawn on paper, or your fingers. Put a finger on the start number, then move one step each time you count. Ask: “What is one more?” and “What is one less?”
Exercise 1C One more and one less
Non-calculatorKey words. One more is the next number. One less is the number just before.
Method. Start at 3. One more is the number after 3.
- Start at 3. Put your finger on the number.Start: 3
- Move one step forward. Each step on the number line is one number.3 + 1 = 4
- Write the answer. 4
Check. Check it: 4 − 1 = 3. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 8. One less is the number before 8.
- Start at 8. Put your finger on the number.Start: 8
- Move one step back. Each step on the number line is one number.8 − 1 = 7
- Write the answer. 7
Check. Check it: 7 + 1 = 8. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 0. One more is the number after 0.
- Start at 0. Put your finger on the number.Start: 0
- Move one step forward. Each step on the number line is one number.0 + 1 = 1
- Write the answer. 1
Check. Check it: 1 − 1 = 0. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 1. One less is the number before 1.
- Start at 1. Put your finger on the number.Start: 1
- Move one step back. Each step on the number line is one number.1 − 1 = 0
- Write the answer. 0
Check. Check it: 0 + 1 = 1. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 2. One more is the number after 2.
- Start at 2. Put your finger on the number.Start: 2
- Move one step forward. Each step on the number line is one number.2 + 1 = 3
- Write the answer. 3
Check. Check it: 3 − 1 = 2. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 6. One more is the number after 6.
- Start at 6. Put your finger on the number.Start: 6
- Move one step forward. Each step on the number line is one number.6 + 1 = 7
- Write the answer. 7
Check. Check it: 7 − 1 = 6. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 9. One more is the number after 9.
- Start at 9. Put your finger on the number.Start: 9
- Move one step forward. Each step on the number line is one number.9 + 1 = 10
- Write the answer. 10
Check. Check it: 10 − 1 = 9. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 4. One less is the number before 4.
- Start at 4. Put your finger on the number.Start: 4
- Move one step back. Each step on the number line is one number.4 − 1 = 3
- Write the answer. 3
Check. Check it: 3 + 1 = 4. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 7. One less is the number before 7.
- Start at 7. Put your finger on the number.Start: 7
- Move one step back. Each step on the number line is one number.7 − 1 = 6
- Write the answer. 6
Check. Check it: 6 + 1 = 7. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 10. One less is the number before 10.
- Start at 10. Put your finger on the number.Start: 10
- Move one step back. Each step on the number line is one number.10 − 1 = 9
- Write the answer. 9
Check. Check it: 9 + 1 = 10. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Method. Each number is one more than the number before it. Use the numbers you can see to find the gaps.
- Look at the numbers before each gap. Counting on in ones means each number is one more than the one before.0, 1, ?, 3, ?, 5
- Count on one from the number before each gap. Add 1 to the number before the gap.Gap 3: 1 + 1 = 2
Gap 5: 3 + 1 = 4 - Write the missing numbers. 2, 4
Check. Read the whole line again: each number is one more than the one before. ✓
Watch out. Check the numbers after the gap too. They should still go up by one.
Method. Each number is one more than the number before it. Use the numbers you can see to find the gaps.
- Look at the numbers before each gap. Counting on in ones means each number is one more than the one before.0, 1, 2, ?, 4, 5, 6, ?, 8, 9, 10
- Count on one from the number before each gap. Add 1 to the number before the gap.Gap 4: 2 + 1 = 3
Gap 8: 6 + 1 = 7 - Write the missing numbers. 3, 7
Check. Read the whole line again: each number is one more than the one before. ✓
Watch out. Check the numbers after the gap too. They should still go up by one.
Key words. One more is the next number. One less is the number just before.
Method. Start at 6. One less is the number before 6.
- Start at 6. Put your finger on the number.Start: 6
- Move one step back. Each step on the number line is one number.6 − 1 = 5
- Write the answer. 5
Check. Check it: 5 + 1 = 6. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Key words. One more is the next number. One less is the number just before.
Method. Start at 9. One more is the number after 9.
- Start at 9. Put your finger on the number.Start: 9
- Move one step forward. Each step on the number line is one number.9 + 1 = 10
- Write the answer. 10
Check. Check it: 10 − 1 = 9. ✓
Watch out. Move one step, not two. Do not write the number you started with.
Method. Count on three numbers, one at a time, starting from 2.
- Start at 2. That is where you begin.2
- Count on three numbers. Say each number as you go.3, 4, 5
- Write the last number. The last number you say is 5.5
Check. Count back from 5 to 2: 5, 4, 3, 2. ✓
Watch out. Do not count the number you start on as one of the three jumps.
Method. Try a number and check. One more than 4 is 5, and 5 is bigger than 4.
- Try an example. Pick any number and find one more than it.One more than 4 is 5.
- Compare the two numbers. Counting on always makes the number bigger.5 is bigger than 4.
- Try another example. Is it true again?One more than 8 is 9, and 9 is bigger than 8.
Check. It works every time, because the next number is always one more. ✓
Watch out. One example is not enough to prove it. Think about what happens when you count on.