What is 1/5 of 4?

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

How to calculate 1/5 of 4?

  1. Multiply the whole number by the numerator of the fraction: 4 × 1 = 4
  2. Divide this result by denominator of the fraction: 4/5 = 0.8

How does it work?

The principle behind finding a fraction of a number, such as 1/5 of 4, is rooted in the method of cross-multiplication.

Consider the following proportion: 1 5 = x 4 (where x represents 1/5 of 4)

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

Thus, 1/5 of 4 is equal to 4/5 (or 0.8 in its decimal form).