Check Subtractions by Using Addition

From any addition fact such as

135 + 423 = 558

 

we can work out two subtraction facts.

 

Here we get

558 - 135 = 423

and

558 - 423 = 135

 

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

 

 

Example 1

Anna says that

 

433 - 115 = 318 

Use addition to check if she is right or wrong.

 

Answer

318 + 115 = 433

So Anna is right.

 

Example 2

Ben says that

 

514 - 325 = 219 

Use addition to check if he is right or wrong.

 

Answer

219 + 325 = 544 not 514

So Ben is wrong.

 

Shall we try some questions on this now?