Question

Tom had a very challenging fraction multiplication problem to do, but his sister said it was really easy to do mentally. Can you fi nd the answer mentally? Explain how.

76/81x 80/76

Answer 1

80/81

Explanation:

Mental multiplication of fractions is often easier if factors common to the numerator and denominator are cancelled.

Here the numerator value of 76 in the first fraction cancels the denominator value of 76 in the second fraction. The remaining numerator factor is 80; the remaining denominator factor is 81, which is mutually prime with 80.

The product is 80/81.