What is 4/9 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 4/9 of 80? We'll show you a straightforward method to achieve that.

How to calculate 4/9 of 80?

  1. Multiply the whole number by the numerator of the fraction: 80 × 4 = 320
  2. Divide this result by denominator of the fraction: 320/9 = 35.555555555556

Since 320/9 is an improper fraction, the result could also be expressed as a mixed number: 35 5/9

How does it work?

The principle behind finding a fraction of a number, such as 4/9 of 80, is rooted in the method of cross-multiplication.

Consider the following proportion: 4 9 = x 80 (where x represents 4/9 of 80)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 4 × 80 = 9 x
  2. Which gives: 320 = 9 x
  3. Divide both sides by 9 to isolate x: 320 9 = 9 x 9
  4. Which gives the result: 320 9 = x

Thus, 4/9 of 80 is equal to 320/9 (or 35.555555555556 in its decimal form).