Question 85

If a certain sum of money doubles itself in 7 years 8 months at simple interest, then what will be the yearly rate of interest (in %)?

Solution

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

=> Interest after 7years 8 months = Rs. $$(2x-x)=Rs.$$ $$x$$

Time period = 7 years 8 months = $$7\frac{8}{12}=\frac{23}{3}$$ years

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

=> Simple interest = $$\frac{P\times r\times t}{100}$$

=> $$\frac{x\times r\times\frac{23}{3}}{100}=x$$

=> $$23r=300$$

=> $$r=\frac{300}{23}=13\frac{1}{23}\%$$

=> Ans - (B)

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