What is 3/4 of 81?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 3/4 of 81? We'll show you a straightforward method to achieve that.

How to calculate 3/4 of 81?

  1. Multiply the whole number by the numerator of the fraction: 81 × 3 = 243
  2. Divide this result by denominator of the fraction: 243/4 = 60.75

Since 243/4 is an improper fraction, the result could also be expressed as a mixed number: 60 3/4

How does it work?

The principle behind finding a fraction of a number, such as 3/4 of 81, is rooted in the method of cross-multiplication.

Consider the following proportion: 3 4 = x 81 (where x represents 3/4 of 81)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 3 × 81 = 4 x
  2. Which gives: 243 = 4 x
  3. Divide both sides by 4 to isolate x: 243 4 = 4 x 4
  4. Which gives the result: 243 4 = x

Thus, 3/4 of 81 is equal to 243/4 (or 60.75 in its decimal form).