3
Make 10 first
Learner’s Book 1: Unit 13, pp. 184–185
GoalUse complements to 10 to add by jumping to 10 first.
New words
complements to 10 · two numbers that make 10 togethersplit · break a number into two smaller numbersregroup · put the parts of a number together in a new way
Explanation
Ten is an easy number to land on. Two numbers that make 10 together are called complements to 10. They are 1 and 9, 2 and 8, 3 and 7, 4 and 6 and 5 and 5. To add 8 + 6, first jump 2 to reach 10. We split the 6 into 2 and 4. Then jump the other 4. 10 + 4 = 14, so 8 + 6 = 14.
Worked examples
Look at the ten frames. 8 counters are in the first frame. 2 of the 6 new counters fill it up to 10. The other 4 go in the next frame. The total is 14.
9 + 4: 9 needs 1 to make 10. Split 4 into 1 and 3. 9 + 1 = 10, then 10 + 3 = 13.
6 + 7: 6 needs 4 to make 10. Split 7 into 4 and 3. 6 + 4 = 10, then 10 + 3 = 13.
Class activity
Pairs to 10: write the numbers 0 to 10 on cards, two of each. Turn them face down. Turn over two cards at a time. If they make 10, keep them and say the sum, like 3 + 7 = 10. Who has the most pairs?
Practice
1
What do we add to 7 to make 10?
3
2
What is 8 + 5? The first jump of 2 reaches 10. How many more do you jump, and where do you land?
3 more. You land on 13, so 8 + 5 = 13.
3
What is 9 + 6? The first jump of 1 reaches 10. Jump the rest of the 6. Where do you land?
Jump 5 more to 15, so 9 + 6 = 15.
4
Look at the frame. What number goes with 4 to make 10?
6