Question

During the eighteenth century, the population of country $X$ increased by $1,000$ percent. During the nineteenth century, the population increased by $500$ percent. Calculate by what percent did the population increase over the two century period.

• A. $1,500\%$
• B. $1,700\%$
• C. $4,900\%$
• D. $6,500\%$

Answer 1

The correct option is D $6,500\%$

Let the population be $n$

After century period, population is $n+10n=11n$.

After another century period, the population is $11n+55n=66n$

Therefore, the population is increased by $\frac{(66-1)n}{n}\times 100=6500$ percent in last two centuries.