What is 1/5 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 1/5 of 18? We'll show you a straightforward method to achieve that.

How to calculate 1/5 of 18?

  1. Multiply the whole number by the numerator of the fraction: 18 × 1 = 18
  2. Divide this result by denominator of the fraction: 18/5 = 3.6

Since 18/5 is an improper fraction, the result could also be expressed as a mixed number: 3 3/5

How does it work?

The principle behind finding a fraction of a number, such as 1/5 of 18, is rooted in the method of cross-multiplication.

Consider the following proportion: 1 5 = x 18 (where x represents 1/5 of 18)

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

Thus, 1/5 of 18 is equal to 18/5 (or 3.6 in its decimal form).