Tuesday, August 30, 2011

Math Skills 9 Estimation

When you are estimating with mixed fractions, how do you tell whether to round down or to round up?  What's the difference between a low fraction and a high fraction?

Consider the numbers (7 and 2/11) and (7 and 7/11).  Here are the simple fractions that have 11 in the denominator:

1/11, 2/11, 3/11, 4/11, 5/11, 6/11, 7/11, 8/11, 9/11, 10/11.

Divide this set into halves, a lower half and a higher half:

low:  1/11, 2/11, 3/11, 4/11, 5/11
If one of these is the fraction part of the number, drop the fraction and round down to 7.
high:  6/11, 7/11, 8/11, 9/11, 10/11
If one of these is the fraction part of the number, round up to 8.




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