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8.08 Multiply fractions and mixed numbers

Lesson

Are you ready?

Do you remember how to multiply fractions?

Find the value of $\frac{1}{3}\cdot\frac{7}{10}$13·710.

Learn

To multiply two fractions, we multiply the numerators (top numbers) to get the new numerator, and we multiply the denominators (bottom number) to get the new denominator.

When the multiplication involves one or more mixed numbers we can still use this method, but we first take one extra step to rewrite the mixed numbers as improper fractions.

For example, let's look at the product $1\frac{3}{8}\times2\frac{1}{3}$138×213. We start by rewriting the mixed numbers as improper fractions:

$1\frac{3}{8}\times2\frac{1}{3}$138×213 $=$= $\frac{11}{8}\times\frac{7}{3}$118×73

Now that we have written both values as improper fractions, we can multiply them using our usual method:

$\frac{11}{8}\times\frac{7}{3}$118×73 $=$= $\frac{11\times7}{8\times3}$11×78×3
  $=$= $\frac{77}{24}$7724


So we have that $1\frac{3}{8}\times2\frac{1}{3}=\frac{77}{24}$138×213=7724. We could also rewrite this as the mixed number $3\frac{5}{24}$3524.

Apply

Question

Find the value of $1\frac{1}{7}\times2\frac{2}{5}$117×225.

Remember!

To multiply mixed numbers, we can first rewrite them as improper fractions and then multiply numerators together and multiply denominators together.

Outcomes

MA.5.FR.2.2

Extend previous understanding of multiplication to multiply a fraction by a fraction, including mixed numbers and fractions greater than 1, with procedural reliability.

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