# Use strategies to add/subtract two digit numbers

Lesson

You might remember that there are several strategies to add and subtract numbers.  Maybe you had a favourite!

In this lesson, you'll use those same strategies to add and subtract two-digit numbers (numbers from $10$10 to $99$99).  Can you see the advantages of using each one?

### Bridge to Tens

You can use the strategy of bridge to ten to add two-digit numbers.  Watch the video below to see why and how it works.   In what ways do you find this strategy useful?

### Compensation

You can also use the compensation strategy to add and subtract two-digit numbers.  See how to use this strategy in the video below.   When might you use this strategy?

### Number Line

Using a number line is another strategy that you can turn to when adding and subtracting two-digit numbers.  What times might using a number line be the best choice?

#### Examples

##### question 1

If $28+20=48$28+20=48, what is the answer to $28+18$28+18?

##### question 2

Use the number line to find the answer to $43+12$43+12.

1. First place the bigger of $43$43 and $12$12 on the number line.

2. Use the position of $43$43 to find the place of $43+12$43+12 on the number line.

##### question 3

What is $41-24$4124?