Question

Between 1965 and 1980, the world population grew at an annual rate of 2%. Using the rule of 72, population is expected to double in

Answer 1

The population is expected to double in 36 years

Explanation:

According to the the rule of 72,

A value is doubled if the product of the annual rate and number of years is 72,

Given,

The annual rate of interest = 2%

Let x be the time in years after 1965,

By the above statement,

The population will double if,

x × 2 = 72 ⇒ x = 36

Hence, the after 36 years since 1965 the population will be doubled,

i.e in 2001. ( ∵ 36 years after 1965 )