Fraction Computation: Lesson 9

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Ask students what they can say about this situation.

I multiplied two fractions with different denominators. Then I added those same two fractions. What can you say about these activities?

I think it’s easier to multiply because you can just multiply the numerators, and multiply the denominators.
When you add the fractions, you can’t just add the numerators; you have to convert these fractions to equivalent ones with a common denominator first.
Usually, when you multiply the fractions, the product is less than the sum of those two fractions. But if you use two improper fractions, the sum might be less than the product. Here’s an example: $\frac{8}{2}$ × $\frac{6}{3}$ = 8 and $\frac{8}{2}$ + $\frac{6}{3}$ = 6.
Sometimes the denominator of both the product and the sum will be the same.

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