Explanation : Simple interest for each year = 40/2 = Rs 20
Compound Interest for first year is Rs 20 and for
second year = 41 – 20 = 21
Thus Rs 20 becomes Rs 21, thus rate of interest can be
calculated
P = Rs 20, SI = Rs 1, T = 1 year
So R = SI × 100/P × T = 1 × 100/20 × 1 = 5%