Question

At what rate percent per annum will a sum of money double itself in 20 years.

• A. 5%
• B. 10%
• C. 7.5%
• D. 15%

Answer 1

The correct option is A 5%

Given, time = 20 years.
Let the sum invested be ₹ 100.
So, the Amount received after 20 years = ₹ 200.

We know that,
Principal + Interest = Amount.
Hence, Interest = Amount - Principal = ₹ (200-100) = ₹ 100.

The Simple Interest earned on a sum of ₹ P for a period of T years at the rate of R% p.a S.I is given by $\frac{P\times R\times T}{100}$.

So, ₹ 100 = $\frac{100\times R\times 20}{100}$
Hence, R = 5%.