Estimating Quotients
You can determine if an answer in division is reasonable by learning to estimate the answers.
Sample
Round the divisor to the nearest 10 or 100, depending on how many digits are in the divisor. In the sample problem, the divisor 27 rounds to 30.
Round the dividend to the nearest 10, 100, or 1,000 so that all of the digits, except the first one are zeros. In the sample problem, the dividend 630 rounds to 600.
Divide 600 by 30. The answer is 20.
Compare your estimate to the exact answer to determine if the exact answer is reasonable.
The estimate of 20 and the exact answer of 23 R9 are close so the estimated answer is reasonably close to the actual answer.
Helpful Hint: The estimate and the exact answer will usually have the same number of digits.
Check Division with Multiplication
Division and multiplication are inverse or opposite operations. You can use multiplication to check your division answer this way.
Do the division problem.
Multiply the quotient times the divisor.
If there is a remainder, add it to the multiplication product.
Compare this answer to the dividend. They should be the same number (630 = 630).
