What is 2/5 of 78?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 2/5 of 78? We'll show you a straightforward method to achieve that.

How to calculate 2/5 of 78?

  1. Multiply the whole number by the numerator of the fraction: 78 × 2 = 156
  2. Divide this result by denominator of the fraction: 156/5 = 31.2

Since 156/5 is an improper fraction, the result could also be expressed as a mixed number: 31 1/5

How does it work?

The principle behind finding a fraction of a number, such as 2/5 of 78, is rooted in the method of cross-multiplication.

Consider the following proportion: 2 5 = x 78 (where x represents 2/5 of 78)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 2 × 78 = 5 x
  2. Which gives: 156 = 5 x
  3. Divide both sides by 5 to isolate x: 156 5 = 5 x 5
  4. Which gives the result: 156 5 = x

Thus, 2/5 of 78 is equal to 156/5 (or 31.2 in its decimal form).