Why Round Decimals?Date: 11/24/97 at 00:13:55 From: Jennifer Subject: Trouble with explaining why we would round decimals Dear Dr. Math, Hi. I am an elementary school major, and I have to explain to a 5th grader why we would want to round decimals. Can you please help? Thanks, Jennifer Date: 11/24/97 at 14:34:30 From: Doctor Mike Subject: Re: Trouble with explaining why we would round decimals Dear Jennifer, This may strike you as a cynical answer but I think it is realistic. A very accurate value of Pi is 3.1415926535898 and a less accurate but still useful value is 3.1416. "A little more than 3" is accurate enough for many people, and "whatever" probably would satisfy most students in a middle school detention room. Rounding is the all-purpose process for anyone who doesn't care to be exact - who doesn't want to "sweat the details". That's okay to a point because there are many different uses for numbers. We have to use decimals at various accuracies, because carpenters and bridge builders and NASA scientists have different needs. A different but related subject is student motivation. Excitement on the part of the teacher is very important, and respect for learning in the family is tremendously important. There are some tricks, though. I'll end by mentioning some I can think of quickly. - If you had a choice between "3.1416 billion" dollars and "Pi billion dollars" which would you choose? The difference can buy a lot of courtside Atlanta Hawks seats. - A batting average of .346 and .354 may seem significant to some people. Rounding to .350 (.35) may satisfy your student, or maybe not. - Was your student interested in the Mars Rover? If so, would she have been irritated if some scientist's sloppy calculations had caused it to crash and burn? - There's always the good old "I'll serve either chocolate pudding or lima beans for dessert, depending on whether you can correctly round 9/16 to the nearest hundredth." - And there's "It's sure hard to know why this is important, so let's just do a few of the homework problems to see how to do them, and then go out for pizza". I sincerely hope some of this has given you something you can use. Best regards, -Doctor Mike, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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