Compatible Number Method for Estimating
Date: 09/10/2001 at 02:17:46 From: Salman Subject: Word problem We are supposed to estimate by using compatible numbers. What is a compatible number, and how does one estimate something like 574/8?
Date: 09/10/2001 at 12:25:30 From: Doctor Peterson Subject: Re: Word problem Hi, Salman. I believe that the phrase "compatible number" in this context refers to a number you can use in place of the dividend to make the division easy, that is, a simple multiple of the divisor. In this case, I would look at the 57 and recognize that it is close to 56, a multiple of 8; therefore, 560/8 is an easy problem that gives a good estimate of 574/8. What I did was essentially to round 574, not to the nearest ten, but to the nearest multiple of 8 by a number with only one non-zero digit. To make an even better estimate, I could then notice that I have subtracted 14 from 574, so I will be subtracting 14/8 from the quotient; this is about 2, so a closer estimate would be 2 less than your answer from the first estimate. But that's not part of the compatible number method itself. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
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