What is 1/8 of 20?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 1/8 of 20? We'll show you a straightforward method to achieve that.

How to calculate 1/8 of 20?

  1. Multiply the whole number by the numerator of the fraction: 20 × 1 = 20
  2. Divide this result by denominator of the fraction: 20/8 = 2.5
  3. Simplify by dividing both the numerator and denominator by their GCD (4):
    • 20/4 = 5
    • 8/4 = 2
  4. Which gives: 5/2

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

How does it work?

The principle behind finding a fraction of a number, such as 1/8 of 20, is rooted in the method of cross-multiplication.

Consider the following proportion: 1 8 = x 20 (where x represents 1/8 of 20)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 1 × 20 = 8 x
  2. Which gives: 20 = 8 x
  3. Divide both sides by 8 to isolate x: 20 8 = 8 x 8
  4. Which gives the result: 20 8 = x (or 5 2 = x )

Thus, 1/8 of 20 is equal to 5/2 (or 2.5 in its decimal form).