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?