Question 59

At what percent of simple interest will a sum of money double itself in 15 years?

Solution

Let sum of money = Rs. $$x$$

=> Amount after 15 years = Rs. $$2x$$

Thus, simple interest = Rs. $$(2x-x)$$ = Rs. $$x$$

Let rate of interest = $$r\%$$

=> S.I. = $$\frac{P \times r \times t}{100}$$

=> $$\frac{x \times r \times 15}{100}=x$$

=> $$15r=100$$

=> $$r=\frac{100}{15}=6\frac{2}{3}\%$$

=> Ans - (B)

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