The population of a town increases 4\% annually but is decreased by emigration annually to the extent of (1/2)\%. What will be the increase percent in 3 years?
(a)9.8
(b)10
(c)10.5
(d)10.8
Answer
Answer (as printed): D
Explanation
Let original population = 100. Population after 3 years $$\begin{aligned} & =100 \times\left(1+\frac{3 \frac{1}{2}}{100}\right)^{3}=100 \times \frac{207}{200} \times \frac{207}{200} \times \frac{207}{200}=110.87 \\ & \therefore \quad \text { Increase }=(110.87-100) \%=10.87 \% \approx 10.8 \% \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.