4
Splitting and equal sums
Learner’s Book 1: Unit 13, pp. 185–187
GoalSplit numbers in different ways and find sums that have the same total.
New words
equal · the same amountnumber fact · a sum we know, like 4 + 3 = 7equals sign (=) · means ‘is the same as’
Explanation
A number can be split into two smaller numbers in different ways. 12 can be 10 and 2, or 8 and 4, or 6 and 6. Different splits give different sums with the same total. We can put an equals sign between them: 8 + 4 = 6 + 6. Both sides make 12. Think of balance scales. If both sides have the same value, the scales balance.
Worked examples
| split | total |
|---|---|
| 10 + 3 | 13 |
| 9 + 4 | 13 |
| 6 + 7 | 13 |
9 + 3 = 7 + 5, because both sides make 12.
8 + 5 = 9 + ? First 8 + 5 = 13. Then 9 + 4 = 13, so the missing number is 4.
Class activity
Equal sums: take a total from 10 to 16 and count out that many beans. Split them into two piles in as many ways as you can. Write each way as a sum. How many different ways did you find?
Practice
1
Split 14 into two parts in two different ways.
Any two, such as 10 + 4 and 7 + 7
2
The scales balance. What total is on each side?
12 on each side: 7 + 5 = 12 and 6 + 6 = 12.
3
Fill in the missing number: 8 + 6 = 7 + ?
7
4
Is 9 + 4 equal to 8 + 6?
No. 9 + 4 = 13 but 8 + 6 = 14.