Step-by-step Maths Level 1: Adding within 20
Part of the Step-by-step Maths Level 1 number stories within 20 chapter. Chapter overview · whole chapter on one page
Adding within 20
To add numbers up to 20, start at the bigger number and count on.
A ten frame helps. Fill the first frame to ten, then count the rest.
Key ideas
- Start at the bigger number.
- Count on the smaller number.
- A full ten frame makes ten. Count the rest.
Method. Start at the bigger number and count on.
- Start at 8. The bigger number is 8.8
- Count on 6. Nine, ten, eleven, twelve, thirteen, fourteen.9, 10, 11, 12, 13, 14
- Write the answer. 14
Check. 6 + 8 = 14. It is the same both ways.
Watch out. Count on, do not start again from one.
Method. Make ten first, then count the rest.
- Make ten. Take 3 from the 9 to make 7 + 3 = 10.7 + 3 = 10
- Count the rest. There are 6 left in the 9.10 + 6
- Write the answer. 16
Check. 9 + 7 = 16. It is the same both ways.
Watch out. Making ten makes adding easier.
Method. More means add.
- Start with 11. Ruby had eleven stamps.11
- Add the 5 more. Count on 5 from 11.11 + 5 = 16
- Write the answer. 16
Check. Count back 5 from 16: 15, 14, 13, 12, 11. It works.
Watch out. Count on from the bigger number.
Watch out
Watch out. Be careful when you cross ten. 14 is one ten and four, not 10 and 14.
Exam tip
Grown-up tip. Use two ten frames or two cups. Fill one to ten, then count the rest. Ask: “How many tens? How many more?”
Exercise 9B Adding within 20
Non-calculatorMethod. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.9
- Count on 9 more. We add 9 to 9.9 + 9
- Write the answer. 18
Check. Count on from the other number too. You get 18 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.11
- Count on 6 more. We add 6 to 11.11 + 6
- Write the answer. 17
Check. Count on from the other number too. You get 17 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.5
- Count on 5 more. We add 5 to 5.5 + 5
- Write the answer. 10
Check. Count on from the other number too. You get 10 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.12
- Count on 8 more. We add 8 to 12.12 + 8
- Write the answer. 20
Check. Count on from the other number too. You get 20 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.7
- Count on 6 more. We add 6 to 7.7 + 6
- Write the answer. 13
Check. Count on from the other number too. You get 13 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.8
- Count on 6 more. We add 6 to 8.8 + 6
- Write the answer. 14
Check. Count on from the other number too. You get 14 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.11
- Count on 5 more. We add 5 to 11.11 + 5
- Write the answer. 16
Check. Count on from the other number too. You get 16 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.15
- Count on 3 more. We add 3 to 15.15 + 3
- Write the answer. 18
Check. Count on from the other number too. You get 18 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.14
- Count on 5 more. We add 5 to 14.14 + 5
- Write the answer. 19
Check. Count on from the other number too. You get 19 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.13
- Count on 5 more. We add 5 to 13.13 + 5
- Write the answer. 18
Check. Count on from the other number too. You get 18 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.15
- Count on 4 more. We add 4 to 15.15 + 4
- Write the answer. 19
Check. Count on from the other number too. You get 19 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.10
- Count on 6 more. We add 6 to 10.10 + 6
- Write the answer. 16
Check. Count on from the other number too. You get 16 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.8
- Count on 6 more. We add 6 to 8.8 + 6
- Write the answer. 14
Check. Count on from the other number too. You get 14 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.15
- Count on 3 more. We add 3 to 15.15 + 3
- Write the answer. 18
Check. Count on from the other number too. You get 18 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.14
- Count on 3 more. We add 3 to 14.14 + 3
- Write the answer. 17
Check. Count on from the other number too. You get 17 both ways.
Watch out. Count on, do not start again from one.
Method. Put the two groups together. Start at the bigger number and count on.
- Start at the bigger number. It is quicker to count on from the bigger one.12
- Count on 6 more. We add 6 to 12.12 + 6
- Write the answer. 18
Check. Count on from the other number too. You get 18 both ways.
Watch out. Count on, do not start again from one.