What is 1/9 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 1/9 of 15? We'll show you a straightforward method to achieve that.

How to calculate 1/9 of 15?

  1. Multiply the whole number by the numerator of the fraction: 15 × 1 = 15
  2. Divide this result by denominator of the fraction: 15/9 = 1.6666666666667
  3. Simplify by dividing both the numerator and denominator by their GCD (3):
    • 15/3 = 5
    • 9/3 = 3
  4. Which gives: 5/3

Since 5/3 is an improper fraction, the result could also be expressed as a mixed number: 1 2/3

How does it work?

The principle behind finding a fraction of a number, such as 1/9 of 15, is rooted in the method of cross-multiplication.

Consider the following proportion: 1 9 = x 15 (where x represents 1/9 of 15)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 1 × 15 = 9 x
  2. Which gives: 15 = 9 x
  3. Divide both sides by 9 to isolate x: 15 9 = 9 x 9
  4. Which gives the result: 15 9 = x (or 5 3 = x )

Thus, 1/9 of 15 is equal to 5/3 (or 1.6666666666667 in its decimal form).