Year 1: One more and one less
Part of the Year 1 numbers to 100 chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
One more and one less
One more is the number that comes next. One less is the number that comes just before. On the 100 square, one more is one step to the right. One less is one step to the left.
Be careful at the end of a row. One more than 39 is 40, because 40 starts the next row.
Key ideas
- One more is the next number. Count on one.
- One less is the number before. Count back one.
- Across a ten: 39 + 1 is 40, and 40 − 1 is 39.
- Check your answer by counting on or back from the number.
Key words. After means one more. Before means one less.
Method. After means one more. Find 39 on the 100 square first.
- Find 39 on the 100 square. 39 is 3 tens and 9 ones.39 = 3 tens and 9 ones
- Move one step on. This number is at the end of a row. The next number starts the next row.39 + 1 = 40
- Write the answer. 40
Check. Count on one from 39 and you say 40. ✓
Watch out. Do not write 39 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 60 on the 100 square first.
- Find 60 on the 100 square. 60 is 6 tens and 0 ones.60 = 6 tens and 0 ones
- Move one step back. Before means one less. Move one step back.60 − 1 = 59
- Write the answer. 59
Check. Count back one from 60 and you say 59. ✓
Watch out. Do not write 60 again. The answer is the number just before.
Method. One less is the number before. One more is the number after.
- Find one less than 50. Count back one from the number.50 − 1 = 49
- Find one more than 50. Count on one from the number.50 + 1 = 51
- Write the answer. 49 and 51
Check. Count in order: 49, 50, 51. ✓
Watch out. Check the number in the middle is the number you started with.
Watch out
Watch out: when a number ends in 9, one more changes the tens. 39 + 1 is 40, not 30.
Exam tip
Grown-up tip. Point to a number on a 100 square. Move one square right for one more, and one square left for one less. Ask: “What is one more than 49?” and see if your child moves into the next row.
Exercise 6D One more and one less
Non-calculatorKey words. After means one more. Before means one less.
Method. After means one more. Find 14 on the 100 square first.
- Find 14 on the 100 square. 14 is 1 ten and 4 ones.14 = 1 ten and 4 ones
- Move one step on. After means one more. Move one step on.14 + 1 = 15
- Write the answer. 15
Check. Count on one from 14 and you say 15. ✓
Watch out. Do not write 14 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 27 on the 100 square first.
- Find 27 on the 100 square. 27 is 2 tens and 7 ones.27 = 2 tens and 7 ones
- Move one step back. Before means one less. Move one step back.27 − 1 = 26
- Write the answer. 26
Check. Count back one from 27 and you say 26. ✓
Watch out. Do not write 27 again. The answer is the number just before.
Key words. After means one more. Before means one less.
Method. After means one more. Find 59 on the 100 square first.
- Find 59 on the 100 square. 59 is 5 tens and 9 ones.59 = 5 tens and 9 ones
- Move one step on. This number is at the end of a row. The next number starts the next row.59 + 1 = 60
- Write the answer. 60
Check. Count on one from 59 and you say 60. ✓
Watch out. Do not write 59 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 70 on the 100 square first.
- Find 70 on the 100 square. 70 is 7 tens and 0 ones.70 = 7 tens and 0 ones
- Move one step back. Before means one less. Move one step back.70 − 1 = 69
- Write the answer. 69
Check. Count back one from 70 and you say 69. ✓
Watch out. Do not write 70 again. The answer is the number just before.
Key words. After means one more. Before means one less.
Method. After means one more. Find 99 on the 100 square first.
- Find 99 on the 100 square. 99 is 9 tens and 9 ones.99 = 9 tens and 9 ones
- Move one step on. This number is at the end of a row. The next number starts the next row.99 + 1 = 100
- Write the answer. 100
Check. Count on one from 99 and you say 100. ✓
Watch out. Do not write 99 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. After means one more. Find 36 on the 100 square first.
- Find 36 on the 100 square. 36 is 3 tens and 6 ones.36 = 3 tens and 6 ones
- Move one step on. After means one more. Move one step on.36 + 1 = 37
- Write the answer. 37
Check. Count on one from 36 and you say 37. ✓
Watch out. Do not write 36 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. After means one more. Find 48 on the 100 square first.
- Find 48 on the 100 square. 48 is 4 tens and 8 ones.48 = 4 tens and 8 ones
- Move one step on. After means one more. Move one step on.48 + 1 = 49
- Write the answer. 49
Check. Count on one from 48 and you say 49. ✓
Watch out. Do not write 48 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. After means one more. Find 90 on the 100 square first.
- Find 90 on the 100 square. 90 is 9 tens and 0 ones.90 = 9 tens and 0 ones
- Move one step on. After means one more. Move one step on.90 + 1 = 91
- Write the answer. 91
Check. Count on one from 90 and you say 91. ✓
Watch out. Do not write 90 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 41 on the 100 square first.
- Find 41 on the 100 square. 41 is 4 tens and 1 one.41 = 4 tens and 1 one
- Move one step back. Before means one less. Move one step back.41 − 1 = 40
- Write the answer. 40
Check. Count back one from 41 and you say 40. ✓
Watch out. Do not write 41 again. The answer is the number just before.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 50 on the 100 square first.
- Find 50 on the 100 square. 50 is 5 tens and 0 ones.50 = 5 tens and 0 ones
- Move one step back. Before means one less. Move one step back.50 − 1 = 49
- Write the answer. 49
Check. Count back one from 50 and you say 49. ✓
Watch out. Do not write 50 again. The answer is the number just before.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 100 on the 100 square first.
- Find 100 on the 100 square. 100 is 10 tens and 0 ones.100 = 10 tens and 0 ones
- Move one step back. Before means one less. Move one step back.100 − 1 = 99
- Write the answer. 99
Check. Count back one from 100 and you say 99. ✓
Watch out. Do not write 100 again. The answer is the number just before.
Key words. After means one more. Before means one less.
Method. After means one more. Find 64 on the 100 square first.
- Find 64 on the 100 square. 64 is 6 tens and 4 ones.64 = 6 tens and 4 ones
- Move one step on. After means one more. Move one step on.64 + 1 = 65
- Write the answer. 65
Check. Count on one from 64 and you say 65. ✓
Watch out. Do not write 64 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 40 on the 100 square first.
- Find 40 on the 100 square. 40 is 4 tens and 0 ones.40 = 4 tens and 0 ones
- Move one step back. Before means one less. Move one step back.40 − 1 = 39
- Write the answer. 39
Check. Count back one from 40 and you say 39. ✓
Watch out. Do not write 40 again. The answer is the number just before.
Key words. After means one more. Before means one less.
Method. After means one more. Find 49 on the 100 square first.
- Find 49 on the 100 square. 49 is 4 tens and 9 ones.49 = 4 tens and 9 ones
- Move one step on. This number is at the end of a row. The next number starts the next row.49 + 1 = 50
- Write the answer. 50
Check. Count on one from 49 and you say 50. ✓
Watch out. Do not write 49 again. The answer is the next number.
Key words. After means one more. Before means one less.
Method. Before means one less. Find 37 on the 100 square first.
- Find 37 on the 100 square. 37 is 3 tens and 7 ones.37 = 3 tens and 7 ones
- Move one step back. Before means one less. Move one step back.37 − 1 = 36
- Write the answer. 36
Check. Count back one from 37 and you say 36. ✓
Watch out. Do not write 37 again. The answer is the number just before.
Key words. To count on is to say the next numbers in order, one more each time.
Method. Start at 45. Say the next number each time, one at a time.
- Start at 45. Put your finger on the number you start from.Start: 45
- Say 10 numbers, one at a time. Each new number is one more than the one before.46, 47, 48, 49, 50, 51, 52, 53, 54, 55
- Write the numbers in order. Write each number you said.46, 47, 48, 49, 50, 51, 52, 53, 54, 55
Check. Count back from 55 to 45 with your finger. The same numbers come again. ✓
Watch out. Do not say 45 again. Start with the number after it.