Word Problem 15

Problem 15: The population of a town increases by 5% annually and its present population is 9261. The population three years ago was;

a. 8.020           b. 8000            c. 9800            d. 10000

Job Exam math, Entrance exam math —


This is interest based problem and requires interest formula for solution.

Here we assume that;

R=Rate of increase in population=5

A=Present population=9261

T= duration of three years =3

P=population three years ago=?

Putting these values in the formula;

A=P[1+\frac{R}{100}] ^{T}

\Rightarrow 9261=P[1+\frac{5}{100}] ^{3}

\Rightarrow 9261=P[\frac{105}{100}] ^{3}

\Rightarrow 9261=P[\frac{105\times105\times105}{100\times100\times100}] ^{3}

\Rightarrow  P=[\frac{100\times100\times100}{105\times105\times105}] ^{3}\times9261}

\Rightarrow  P=8000

So, the population three years ago was 8000