Question

The rate of simple interest per annum at which a sum of money doubles itself in 20 years is

1. 5%
2. 7%
3. 8%
4. 6%

Answer 1

Correct Answer - Option 1 : 5%

Given: 

Money gets doubled in 20 years.

Formula used:

Simple Interest = (Principal × Rate × Time)/100

Calculation:

Time = 20 year 

Amount double = 2p

Interest = 2p - p = p

Rate = (S.I. × 100)/(Time × Principal)

Rate = (p × 100)/(20 × p)

Rate = 5%

∴ The rate of interest is 5%