How do you use compatible numbers when checking division answers?


Quick Answer

When checking division answers, students can use compatible numbers to estimate if the quotient part of the answer is reasonable. The procedure entails using a dividend and a divisor that are compatible and close enough to the ones of the original division problem. This gives an estimated quotient students can compare with their actual answer.

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Full Answer

When doing division problems, compatible numbers refers to numbers that can be divided easily using mental math, such as 12 divided by 3 or 65 divided by 5. Compatible numbers are usually referred to as friendly numbers. With this method, students can estimate the quotient for a division problem easily to check answers. As an example, find compatible numbers and quotient for the division problem 574 divided by 8.

  1. Find the quotient using compatible numbers
  2. Look at the dividend and divisor and find compatible numbers that are close to them. Do this by finding a multiple of 8 that is close to 574, which is 560. Divide 560 by 8 to find the quotient as 70, which means that the answer to the division problem should be close to this estimation.

  3. Divide the dividend by the divisor given in the actual division problem
  4. Perform the division to find the answer as 71 6/8 that is 71 3/4 or 71.75. Check the quotient 71 of this division and compare it to the estimated quotient of 70, and this shows that the answer is in fact reasonable or very close to the estimate. Note that the fraction 3/4 is the remainder.

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