Multiply mixed numbers by an integer
To multiply a mixed number by an integer there are two methods.
Take a look at these examples to see both methods in practice.
Example 1
Ayaan has 2 \(\frac{6}{8}\) pizzas. He needs three times this amount. How many pizzas does he need?
Our calculation is: 2 \(\frac{6}{8}\) x 3 = ?
To solve this calculation, we are going to use the partition method. It can help to draw the fractions in a bar model.
Step 1
Partition 2 \(\frac{6}{8}\)into the whole number and the fraction. The whole number is 2 and the fraction is \(\frac{6}{8}\)
Step 2
Multiply the whole number by 3.
2 x 3 = 6
Step 3
Now multiply the fraction \(\frac{6}{8}\) by 3.
\(\frac{6}{8}\) x 3 =\(\frac{18}{8}\)
\(\frac{18}{8}\)= 2 \(\frac{2}{8}\)
Step 4
Add the totals from step 2 and step 3 together:
6 + 2 \(\frac{6}{8}\) = 8 \(\frac{6}{8}\)
The answer to the calculation is: 2 \(\frac{6}{8}\) x 3 = 8 \(\frac{2}{8}\).
Ayaan will need 9 pizzas.
Example 2
In this example, we will convert our mixed number into an improper fraction.
3 \(\frac{3}{5}\) x 4 = ?
Step 1
Convert the mixed fraction into an improper fraction.
3 \(\frac{3}{5}\) = \(\frac{18}{5}\)
Step 2:
When multiplying fractions we multiply the numerator (top number) by the integer (whole number). The denominator (bottom number) stays the same.
\(\frac{18}{5}\) x 4 = \(\frac{72}{5}\)
Step 3
Convert the improper fraction to a mixed number.
\(\frac{72}{5}\) = 14 \(\frac{2}{5}\)
The answer to our calculation:3 \(\frac{3}{5}\) x 3 = 14 \(\frac{2}{5}\)
When you're multiplying fractions by an integer (or a whole number) you multiply the numerator of the fraction by the whole number and the denominator stays the same.
Activity
Quiz
Test what you have learnt in this guide by having a go at this quiz.
You may need a pencil and paper to jot down your working out.
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