Addition and Subtraction

Lesson

There are several strategies for adding and subtracting numbers. One strategy you can use is to split numbers apart and make pairs to $10$10.

Pairs to $10$10 are two numbers that add together to make $10$10. You might find this strategy helpful because it changes a problem like $9+6$9+6 to something like $10+5$10+5. Adding $10$10 can be much quicker!

Watch the video below to see how to change an addition problem using the Bridge to 10 strategy. Do you think this strategy makes addition easier?

How many more do we need to add to $9$9 to get to $10$10?

We want to find $7+6$7+6.

First, split up $6$6 so that we have a pair to $10$10.

$7$7 $+$+ $6$6 $=$= ?? $|$| $\frown$⌢ $7$7 $+$+ $\editable{}$ $+$+ $\editable{}$ $=$= ?? $\smile$⌣ $10$10 Use the bridge to ten above to find $7+6$7+6.

We want to find $37+5$37+5.

First, split up $5$5 so that we have a pair to $10$10.

$37$37 $+$+ $5$5 $=$= ?? $|$| $\frown$⌢ $37$37 $+$+ $\editable{}$ $+$+ $\editable{}$ $=$= ?? $\smile$⌣ $40$40 Use the bridge to ten above to find $37+5$37+5.

Use simple additive strategies with whole numbers and fractions

Generalise that whole numbers can be partitioned in many ways