A sum of money becomes 5 times itself in 20 years at a certain rate of simple interest. In how many years will it become 9 times itself at the same rate?
Show answer & explanation
Correct answer: B
Explanation
Given:
Amount in 20 years = 5P
By formula:
At simple interest
A = P(1 + RT/100)
5P = P(1 + RT/100)
1 + RT/100 = 5
RT/100 = 4
20R/100 = 4
R = 20%
9P = P(1 + 20T/100)
1 + 20T/100 = 9
20T/100 = 8
T = 40
Time = 40 years