What is 9/10 of 18?

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

How to calculate 9/10 of 18?

  1. Multiply the whole number by the numerator of the fraction: 18 × 9 = 162
  2. Divide this result by denominator of the fraction: 162/10 = 16.2
  3. Simplify by dividing both the numerator and denominator by their GCD (2):
    • 162/2 = 81
    • 10/2 = 5
  4. Which gives: 81/5

Since 81/5 is an improper fraction, the result could also be expressed as a mixed number: 16 1/5

How does it work?

The principle behind finding a fraction of a number, such as 9/10 of 18, is rooted in the method of cross-multiplication.

Consider the following proportion: 9 10 = x 18 (where x represents 9/10 of 18)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 9 × 18 = 10 x
  2. Which gives: 162 = 10 x
  3. Divide both sides by 10 to isolate x: 162 10 = 10 x 10
  4. Which gives the result: 162 10 = x (or 81 5 = x )

Thus, 9/10 of 18 is equal to 81/5 (or 16.2 in its decimal form).