What is 4/10 of 77?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 4/10 of 77? We'll show you a straightforward method to achieve that.

How to calculate 4/10 of 77?

  1. Multiply the whole number by the numerator of the fraction: 77 × 4 = 308
  2. Divide this result by denominator of the fraction: 308/10 = 30.8
  3. Simplify by dividing both the numerator and denominator by their GCD (2):
    • 308/2 = 154
    • 10/2 = 5
  4. Which gives: 154/5

Since 154/5 is an improper fraction, the result could also be expressed as a mixed number: 30 4/5

How does it work?

The principle behind finding a fraction of a number, such as 4/10 of 77, is rooted in the method of cross-multiplication.

Consider the following proportion: 4 10 = x 77 (where x represents 4/10 of 77)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 4 × 77 = 10 x
  2. Which gives: 308 = 10 x
  3. Divide both sides by 10 to isolate x: 308 10 = 10 x 10
  4. Which gives the result: 308 10 = x (or 154 5 = x )

Thus, 4/10 of 77 is equal to 154/5 (or 30.8 in its decimal form).