What is 9/10 of 86?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 9/10 of 86? We'll show you a straightforward method to achieve that.

How to calculate 9/10 of 86?

  1. Multiply the whole number by the numerator of the fraction: 86 × 9 = 774
  2. Divide this result by denominator of the fraction: 774/10 = 77.4
  3. Simplify by dividing both the numerator and denominator by their GCD (2):
    • 774/2 = 387
    • 10/2 = 5
  4. Which gives: 387/5

Since 387/5 is an improper fraction, the result could also be expressed as a mixed number: 77 2/5

How does it work?

The principle behind finding a fraction of a number, such as 9/10 of 86, is rooted in the method of cross-multiplication.

Consider the following proportion: 9 10 = x 86 (where x represents 9/10 of 86)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 9 × 86 = 10 x
  2. Which gives: 774 = 10 x
  3. Divide both sides by 10 to isolate x: 774 10 = 10 x 10
  4. Which gives the result: 774 10 = x (or 387 5 = x )

Thus, 9/10 of 86 is equal to 387/5 (or 77.4 in its decimal form).