Mixed fractions are comprised of both a whole number and a fraction. Mixed fractions can be added, subtracted, divided or multiplied. The ability to estimate products of mixed fractions allows students to quickly calculate problems, and gives them a reference they can use to check the accuracy of their work. Estimations that differ greatly from the actual answer can serve as a warning to students that there may be an error in their computations.
Round the fraction portions of the mixed fractions to the nearest whole number. For example, if your mixed fractions are 3 3/4 x 2 2/5, round 3/4 up to one and round 2/5 down to zero.
Add the rounded fractions to the whole numbers of each mixed fraction. Using the previous example, 3/4 rounded up to one would be added to the whole number three, giving a sum of four. The fraction 2/5 rounded down to zero and added to the whole number two would equal two.
Multiply the two new whole numbers together to give you an estimated product for your mixed fractions. Multiply 4 x 2, which gives you an estimated product of eight. The actual product of 3 3/4 x 2 2/5 is 6 6/20, which is close to eight.
- "Everyday Mathematics Student Reference Book: Grade 5"; The University of Chicago School Mathematics Project; 2007
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