A district has 64000 inhabitants. If the population increases at the rate of $2 \frac{1}{2} \%$ per annum, then the number of inhabitants at the end of 3 years will be
(a)68911
(b)68921
(c)69200
(d)70000
Answer
Answer (as printed): B
Explanation
Population after 3 years $=64000 \times\left(1+\frac{5}{2 \times 100}\right)^{3}$ $$=\left(64000 \times \frac{41}{40} \times \frac{41}{40} \times \frac{41}{40}\right)=68921 .$$
Explanation as extracted from the printed page; notation may be imperfect.