Add three addends efficiently using a range of strategies | Maths

Starter quiz

6 + 4 + 2 =

10

12 ✓

14

16
6 + 6 + 2 =

'14' ✓
Match the equation to the sum.

9 + 1 + 3

⇔

13 ✓

1 + 9 + 2

⇔

12 ✓

9 + 1 + 4

⇔

14 ✓

9 + 5 + 1

⇔

15 ✓
What is the sum of the numbers in the bar model?

13

15 ✓

17

19
What addend is missing from the bar model?

6 ✓

7

8

9
The missing numbers from this bar model both have the same value. What are both numbers?

5 ✓

6

7

10

How would you find the sum of these calculations? Match them to the strategy you would use.

6 + 2 + 4

⇔

pairs that total 10 ✓

5 + 6 + 2

⇔

near doubles ✓

6 + 2 + 6

⇔

doubles ✓
What is the sum of the numbers in the bar model?

13

15

17

18 ✓
Match up the equations to the correct sum.

4 + 4 + 3

⇔

11 ✓

5 + 4 + 5

⇔

14 ✓

6 + 5 + 2

⇔

13 ✓

2 + 4 + 6

⇔

12 ✓
What is the missing addend in the bar model?

5

7 ✓

8

9
What is 8 + 3 + 8?

16

17

18

19 ✓
Which calculations could be used to make this equation correct?

4 + 6 + 6 ✓

8 + 8 + 2

9 + 2 + 6

6 + 7 + 3 ✓

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Using commutativity allows us to simplify a problem with three addends.
Using known facts allows us to add three addends efficiently.
Rearranging the addends to identify the pairs that total 10 allows us to add efficiently.

Children rely on one strategy for adding to find a sum and do not consider the values.

Discuss when it is most efficient to use doubles, near doubles, number pairs to 10. Model efficient approaches.

Addend - A number added to another.
Commutative - Addition is commutative. This means the order of the addends can be changed without changing the calculation or sum.
Equation - An equation is used to show that one number or calculation is equal to another.
Sum - The total when numbers are added together.