What is 9/10 of 5?

Often, in mathematics or everyday life, we need to find a fraction of a given number. For instance, how would you quickly calculate 9/10 of 5? We'll show you a straightforward method to achieve that.

How to calculate 9/10 of 5?

  1. Multiply the whole number by the numerator of the fraction: 5 × 9 = 45
  2. Divide this result by denominator of the fraction: 45/10 = 4.5
  3. Simplify by dividing both the numerator and denominator by their GCD (5):
    • 45/5 = 9
    • 10/5 = 2
  4. Which gives: 9/2

Since 9/2 is an improper fraction, the result could also be expressed as a mixed number: 4 1/2

How does it work?

The principle behind finding a fraction of a number, such as 9/10 of 5, is rooted in the method of cross-multiplication.

Consider the following proportion: 9 10 = x 5 (where x represents 9/10 of 5)

  1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: 9 × 5 = 10 x
  2. Which gives: 45 = 10 x
  3. Divide both sides by 10 to isolate x: 45 10 = 10 x 10
  4. Which gives the result: 45 10 = x (or 9 2 = x )

Thus, 9/10 of 5 is equal to 9/2 (or 4.5 in its decimal form).