What is 5/7 of 90?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 5/7 of 90? We'll show you a straightforward method to achieve that.

How to calculate 5/7 of 90?

  1. Multiply the whole number by the numerator of the fraction: 90 × 5 = 450
  2. Divide this result by denominator of the fraction: 450/7 = 64.285714285714

Since 450/7 is an improper fraction, the result could also be expressed as a mixed number: 64 2/7

How does it work?

The principle behind finding a fraction of a number, such as 5/7 of 90, is rooted in the method of cross-multiplication.

Consider the following proportion: 5 7 = x 90 (where x represents 5/7 of 90)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 5 × 90 = 7 x
  2. Which gives: 450 = 7 x
  3. Divide both sides by 7 to isolate x: 450 7 = 7 x 7
  4. Which gives the result: 450 7 = x

Thus, 5/7 of 90 is equal to 450/7 (or 64.285714285714 in its decimal form).