In order to solve this problem we need to use the operation of subtraction.
Why did we add 100 to 70?
A shorter way to solve is as follows:
978
- 786
192 --> difference
Start working on the rightmost column, the ones place value. Take 6 ones from 8 ones. In the difference, write 2 in the ones column. Since 7 tens is lesser than 8 tens, we take 100 from 9 hundreds and add it to 17 tens. And so we have 17 tens: 17 - 8 = 9. Write 9 in the tens column in the difference. 9 hundreds become 8 hundreds and 9 - 8 = 1.
To check our answer, we use addition, since it is the inverse operation of subtraction. We add the difference and the subtrahend and see if we get the minuend.
192
+ 786
978
Check if the the properties of addition holds for subtraction of whole numbers.
a. Is 4 - 7 a whole number?
b. Is 8 - 3 = 3 - 8 ?
c. Is (1 - 6) - 8 = 1 - (6 - 8)?
If your answer to a is no, then you're correct. A negative number is not a whole number. As for items b and c, it is still no! The properties of addition of whole numbers do not hold true in subtraction of whole numbers..
Try the following: Subtract and check.
a. 23
12
b. 572
192
c. 7,956
4,785
