What is 8/9 of 80?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 8/9 of 80? We'll show you a straightforward method to achieve that.

How to calculate 8/9 of 80?

  1. Multiply the whole number by the numerator of the fraction: 80 × 8 = 640
  2. Divide this result by denominator of the fraction: 640/9 = 71.111111111111

Since 640/9 is an improper fraction, the result could also be expressed as a mixed number: 71 1/9

How does it work?

The principle behind finding a fraction of a number, such as 8/9 of 80, is rooted in the method of cross-multiplication.

Consider the following proportion: 8 9 = x 80 (where x represents 8/9 of 80)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 8 × 80 = 9 x
  2. Which gives: 640 = 9 x
  3. Divide both sides by 9 to isolate x: 640 9 = 9 x 9
  4. Which gives the result: 640 9 = x

Thus, 8/9 of 80 is equal to 640/9 (or 71.111111111111 in its decimal form).