Checking calculations by doing the inverse
Miss Hall has completed some subtraction calculations. However, she is not sure whether they are correct or not.
Check Miss Hall's Homework by doing the inverse.
What is the inverse to subtraction?
That's right! It's addition.
+ is the inverse to -
So if 1000 - 250 = 750 then 750 + 250 = 1000.
Also, if 1000 - 750 = 250 then 250 + 750 = 1000.
Miss Hall's Homework
Are Miss Hall's calculations correct or incorrect?
1. Copy out the subtraction calculation.
2. Write the inverse addition calculation.
3. Use column addition to check if the calculation is correct or incorrect.
4. Put a tick next to the calculation if it is correct or a cross if it is incorrect.
1. 1735 - 324 = 1311
2. 6781 - 3454 = 3327
3. 9917 - 1089 = 8828
4. 7345 - 2305 = 5040
5. 3256 - 1829 = 1417