How to multiply and divide fractions

Multiplication

Example


When multiplying 2 fractions, we multiply the two numerators together and the two denominators together. The new numerator is the product of the numerator in the first fraction and the second one. The new denominator is the product of the denominator in the first fraction and the second one.


In the illustration above, the blue part of the pie represents 1/3. The blue section next to it shows the 1/3 piece divided into 2 equal parts. Choosing one of these parts gives us the last section which is 1/6.

Example


When we multiply a whole number by a fraction, we multiply the whole number by the numerator of the fraction. The denominator stays the same. The new result is a fraction in which the numerator has the product of the whole number and the fraction's numerator, the denominator has the fraction's denominator.






RULE FOR MULTIPLYING FRACTIONS

The product of two fractions is a fraction whose numerator is the product of the numerators of the given factors (A/B) and (C/D) and the denominator is the product of the denominators of the given fractions.



Division

Example

2 ÷ 1/3

When we divide a whole number by a fraction, we multiply the whole number with the inverse of the fraction. The inverse of a fraction is created by substituting the numerator for the denominator and the denominator for the numerator. In this example, the inverse of 1/3 is 3/1. And the product of 2 and 3 is 6.

How many 1/3's are there in 2?

2 contains six 1/3's.

Example

1/2 ÷ 1/3

When we divide fractions, we multiply the first fraction with the inverse of the second fraction. In this example, the inverse of 1/3 is 3/1.

How many 1/3's are there in 1/2?

1/2 contains one and a half 1/3's.


RULE FOR DIVIDING FRACTIONS

To divide fraction A/B by C/D, multiply A/B by the inverse of C/D which is D/C.