What is 4/8 of 40?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 4/8 of 40? We'll show you a straightforward method to achieve that.

How to calculate 4/8 of 40?

  1. Multiply the whole number by the numerator of the fraction: 40 × 4 = 160
  2. Divide this result by denominator of the fraction: 160/8 = 20
  3. Simplify by dividing both the numerator and denominator by their GCD (8):
    • 160/8 = 20
    • 8/8 = 1
  4. Which gives: 20/1

How does it work?

The principle behind finding a fraction of a number, such as 4/8 of 40, is rooted in the method of cross-multiplication.

Consider the following proportion: 4 8 = x 40 (where x represents 4/8 of 40)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 4 × 40 = 8 x
  2. Which gives: 160 = 8 x
  3. Divide both sides by 8 to isolate x: 160 8 = 8 x 8
  4. Which gives the result: 160 8 = x (or 20 1 = x )

Thus, 4/8 of 40 is equal to 20/1 (or 20 in its decimal form).