At r% per annum a sum doubles after 20 years. The rate of interest per annum is :
Posted on 15-04-2023
Ques - At r% per annum a sum doubles after 20 years. The rate of interest per annum is :
(a) 4%
(b) 5%
(c) 8%
(d) 10%
Solution -
Given,
Principal = P
Amount = 2P (double itself)
S.I = Amount - Principal
S.I = 2P - P
S.I = P
R = r
T = 20
S.I = (P×R×T) / 100
P = (P × r × 20) / 100
R = 100 / 20
R = 5
Therefore,
The rate of interest per annum is 5%
Hence,
The correct answer is option (b) 5%.
Thank You