Use Addition to Check Subtractions

From any addition fact such as

1,300 + 5,200 = 6,500

 

we can work out two subtraction facts.

 

Here we get:

6,500 - 1,300 = 5,200

and

6,500 - 5,200 = 1,300

 

This is handy because we can use additions to check subtractions.

 

Example 1

Ahmed says that

 

2,800 - 1,100 =

1,700

 

Use addition to check if he is right or wrong.

 

Answer

1,700 + 1,100 = 2,800

So Ahmed is right.

 

 

Example 2

Bill says that

 

6,500 - 3,700 =

3,200

 

Use addition to check if he is right or wrong.

 

Answer

3,200 + 3,700 = 6,900 not 6,500

So Bill is wrong.

 

 

Let's have a go at some questions on this now.