Question

A sum of money doubles itself after 10 years at a certain rate of interest. What is the rate of simple interest?

• A. 15%
• B. 12%
• C. 9%
• D. 10%

Answer 1

The correct option is D 10%

Let the sum be x
Let the rate of interest be r
Principle=x, Rate of interest= r, Time= 10 years
Interest for 10 years$=\frac{P\times T\times R}{100}=\frac{x\times 10\times r}{100}$
Amount doubles after 10 years i.e 2x
Amount = Principle + Interest
$2x=x+\frac{x\times 10\times r}{100}x=\frac{x\times 10\times r}{100}r=\frac{100}{10}r=10$
Hence rate of interest = 10 %