Step-by-step Maths Level 1: The number before and the number after
Part of the Step-by-step Maths Level 1 before, after and between chapter. Chapter overview · whole chapter on one page
The number before and the number after
The number after is one more. The number before is one less.
Think of the number line. After is to the right. Before is to the left.
Key ideas
- The number after is one more.
- The number before is one less.
- Before is to the left on a number line.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.10
- Count back one. Say the number that comes just before.10 - 1 = 9
- Write the answer. 9
Check. Count on one: 9 add 1 is 10. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.16
- Count on one. Say the number that comes next.16 + 1 = 17
- Write the answer. 17
Check. Count back one: 17 take away 1 is 16. It works.
Watch out. One more is the next number, not the same number.
Method. The number before means one less.
- Start at 20. We begin with the number we are given.20
- Count back one. The number before is one less.20 - 1 = 19
- Write the answer. 19
Check. Count on one from 19: 20. It works.
Watch out. Do not say 21. That is after 20.
Watch out
Watch out. Before means less, after means more. Check which way you move on the number line.
Exam tip
Grown-up tip. Say a number, then ask “what comes before?” and “what comes after?” Use stairs or a number track to show left and right.
Exercise 3A Before and after
Non-calculatorMethod. One less means the number just before when we count back.
- Start at the number. We begin where we are.14
- Count back one. Say the number that comes just before.14 - 1 = 13
- Write the answer. 13
Check. Count on one: 13 add 1 is 14. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.1
- Count on one. Say the number that comes next.1 + 1 = 2
- Write the answer. 2
Check. Count back one: 2 take away 1 is 1. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.17
- Count back one. Say the number that comes just before.17 - 1 = 16
- Write the answer. 16
Check. Count on one: 16 add 1 is 17. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.11
- Count on one. Say the number that comes next.11 + 1 = 12
- Write the answer. 12
Check. Count back one: 12 take away 1 is 11. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.5
- Count back one. Say the number that comes just before.5 - 1 = 4
- Write the answer. 4
Check. Count on one: 4 add 1 is 5. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.8
- Count on one. Say the number that comes next.8 + 1 = 9
- Write the answer. 9
Check. Count back one: 9 take away 1 is 8. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.12
- Count back one. Say the number that comes just before.12 - 1 = 11
- Write the answer. 11
Check. Count on one: 11 add 1 is 12. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.6
- Count on one. Say the number that comes next.6 + 1 = 7
- Write the answer. 7
Check. Count back one: 7 take away 1 is 6. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.19
- Count back one. Say the number that comes just before.19 - 1 = 18
- Write the answer. 18
Check. Count on one: 18 add 1 is 19. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.6
- Count on one. Say the number that comes next.6 + 1 = 7
- Write the answer. 7
Check. Count back one: 7 take away 1 is 6. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.12
- Count back one. Say the number that comes just before.12 - 1 = 11
- Write the answer. 11
Check. Count on one: 11 add 1 is 12. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.1
- Count on one. Say the number that comes next.1 + 1 = 2
- Write the answer. 2
Check. Count back one: 2 take away 1 is 1. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.10
- Count back one. Say the number that comes just before.10 - 1 = 9
- Write the answer. 9
Check. Count on one: 9 add 1 is 10. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.16
- Count on one. Say the number that comes next.16 + 1 = 17
- Write the answer. 17
Check. Count back one: 17 take away 1 is 16. It works.
Watch out. One more is the next number, not the same number.
Method. One less means the number just before when we count back.
- Start at the number. We begin where we are.15
- Count back one. Say the number that comes just before.15 - 1 = 14
- Write the answer. 14
Check. Count on one: 14 add 1 is 15. It works.
Watch out. One less is the number before, not the number after.
Method. One more means the next number when we count on.
- Start at the number. We begin where we are.16
- Count on one. Say the number that comes next.16 + 1 = 17
- Write the answer. 17
Check. Count back one: 17 take away 1 is 16. It works.
Watch out. One more is the next number, not the same number.