Page 82 - Start Up Mathematics_5

5 Fractions—

Multiplication and Division

Let’s Recall ...

• To reduce a fraction to its lowest term, we cancel out the common factors
from the numerator and the denominator.
• Multiplication is repeated addition.

• Division is repeated subtraction.

Multiplication of Fractions with Whole Numbers
1
The fraction can be represented as shown.
4

1
Now let’s find out what 3 × is.
4
We know that multiplication is repeated addition. Thus,
1 1 1 1 1 + 1 + 1 3 3 × 1
3 × = + + = = =
4 4 4 4 4 4 4

1 + 1 + 1 = 3
4 4 4 4

Thus to multiply a fraction by a whole number, we multiply the whole number by the
numerator of the fraction and keep the denominator as it is.

4
Example 1: Multiply 7 by .
5
4 7 × 4 28
Solution: 7 × = = (improper fraction)
5 5 5 Remember
3
= 5 (mixed fraction) While multiplying a fraction
5 with a whole number,
Fraction of a Whole Number always express your answer

2 in the lowest term.
Example 2: What is of 6?
3
2 2 2 × 6 12
Solution: of 6 = × 6 = = = 4
3 3 3 3
2
So, of 6 = 4.
3

74