Why Estimate?Date: 08/16/2002 at 11:14:49 From: Stephanie Subject: Estimation Estimate to the nearest thousand a solution to Dave's subtraction problem. The numbers are: 6,107 -2,980 ----- 4,127 I just don't know how to estimate. Date: 08/16/2002 at 12:10:25 From: Doctor Peterson Subject: Re: Estimation Hi, Stephanie. Assuming that 4,127 is "Dave's" answer to the problem, it illustrates why it can be very important to estimate - it's wrong, it's an easy mistake to make, and it would have a huge effect on whatever he uses the number for, from spending money to building a house. And estimating makes it easy to see the error! To estimate to the nearest thousand, the natural thing to do is to round the numbers you are adding to the nearest thousand. Which of these numbers is closest to 6,107? 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Which of those numbers is closest to 2,980? Now subtract those much simpler numbers, and the result is your answer. Sometimes you can get a better estimate by thinking about how much you increased or decreased each number when you rounded them, and how that will affect the result; but in this case the difference of the rounded numbers is good enough. If you need more information on rounding, see our FAQ: Rounding Numbers http://mathforum.org/dr.math/faq/faq.rounding.html For more on estimation, see Estimating Sums By Rounding http://mathforum.org/library/drmath/view/59021.html If you need more help, please write back and show me how far you got. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/ |
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