The formula below gives t, the approximate time in years it takes a population to double if the annual growth rate is r percent.

t=70/r

according to this formula, about how long will it take a population to double if the annual growth rate is 3.2%?

hint: do not convert the growth rate to a decimal before dividing.

a. 22 years
b. 26 years
c. 18 years
d. 30 years

0.4934

Explanation:

To obtain the area of the shaded region under then curve :

P(-2.48 < Z < 0) = P(Z < 0) - P(Z < - 2.48)

To obtain P( Z < x) = (x - μ) / s

Therefore :

P(Z < 0) - P(Z < - 2.48)

Using a Z probability calculator :

P(Z < 0) = 0.5

P(Z < - 2.48) = 0.0065691

Hence,

P(Z < 0) - P(Z < - 2.48) = 0.5 - 0.0065691

Therefore the shaded area under the normal probability curve is = 0.5 - 0.0065691 = 0.4934309

P(Z < 0) - P(Z < - 2.48) = 0.4934