What is 9/10 of 15?

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 15? We'll show you a straightforward method to achieve that.

How to calculate 9/10 of 15?

  1. Multiply the whole number by the numerator of the fraction: 15 × 9 = 135
  2. Divide this result by denominator of the fraction: 135/10 = 13.5
  3. Simplify by dividing both the numerator and denominator by their GCD (5):
    • 135/5 = 27
    • 10/5 = 2
  4. Which gives: 27/2

Since 27/2 is an improper fraction, the result could also be expressed as a mixed number: 13 1/2

How does it work?

The principle behind finding a fraction of a number, such as 9/10 of 15, is rooted in the method of cross-multiplication.

Consider the following proportion: 9 10 = x 15 (where x represents 9/10 of 15)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 9 × 15 = 10 x
  2. Which gives: 135 = 10 x
  3. Divide both sides by 10 to isolate x: 135 10 = 10 x 10
  4. Which gives the result: 135 10 = x (or 27 2 = x )

Thus, 9/10 of 15 is equal to 27/2 (or 13.5 in its decimal form).