 Lesson 5 -1:. A benchmark is a number that is easy to use when you estimate. When estimating the sums and differences of fractions, we use the benchmarks.

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Lesson 5 -1:

A benchmark is a number that is easy to use when you estimate. When estimating the sums and differences of fractions, we use the benchmarks 0, ½, and 1. (another chart on page 249 in textbook)

 Change each fraction to 0, ½, or 1.  Add or subtract. 5 11 + 3 25 + ½ 0= ½

+ 7 15 4 9 + ½ ½ = 1

 If you have mixed numbers, then round the fraction part up to 1 or down to 0.  If the fraction is greater than ½, then round up to 1.  If it is less than ½, then round down to 0.

3 4 1510 1 8 16 10 = 6

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