Question

Hello! At what rate per cent per annum simple interest will a sum double itself in 10 years?
(a) 8% (b) 10% (c) 12% (d) 12 1/2

Answer 1

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Answer 2

Let the Principle be Rs. x

Since the principle doubles

Amount = Rs. 2x

Time = 10 years

Simple Interest = Amount - Principle

Simple Interest = 2x - x = Rs. x

We know Simple Interest = Principle * Time * Rate of interest / 100

x = x * 10 * R/100

x = 10x * R/100

x * 100 = 10x * R

100x = 10x * R

100x/10x = R

R = 10%

So Rate of interest = (b) 10%