What is 9/7 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 9/7 of 81? We'll show you a straightforward method to achieve that.

How to calculate 9/7 of 81?

  1. Multiply the whole number by the numerator of the fraction: 81 × 9 = 729
  2. Divide this result by denominator of the fraction: 729/7 = 104.14285714286

Since 729/7 is an improper fraction, the result could also be expressed as a mixed number: 104 1/7

How does it work?

The principle behind finding a fraction of a number, such as 9/7 of 81, is rooted in the method of cross-multiplication.

Consider the following proportion: 9 7 = x 81 (where x represents 9/7 of 81)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 9 × 81 = 7 x
  2. Which gives: 729 = 7 x
  3. Divide both sides by 7 to isolate x: 729 7 = 7 x 7
  4. Which gives the result: 729 7 = x

Thus, 9/7 of 81 is equal to 729/7 (or 104.14285714286 in its decimal form).