Topper's Approach 2

1. If a sum of money at simple interest doubles in 12 years, the rate of interest per annum is: 
a) 16 2/3
b) 7.5%
c) 8 1/3%
d) 10%
 
 
Answer: c
 
2. An amount of money invested on simple interest becomes 5 times of itself in 16 years. What is the rate of interest per annum?
a) 15%
b) 20%
c) 25%
d) 30%
 
 
Answer: c