A sum becomes 2.5 times of itself in 5 years under simple interest. In how many years will it become 5 times itself at the same rate?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 13 years.
Let principal = P and rate of interest = R%
Amount = P + SI = 2.5P
⇒ SI = 1.5P
SI = (P × R × T)/100
⇒ 1.5P = (P × R × 5)/100
⇒ 5PR/100 = 1.5P
⇒ 150 = 5R
⇒ R = 150/5 = 30% per annum
Now for 5P: SI = 5P - P = 4P
⇒ 4P = (P × 30 × T)/100
⇒ 4 = 0.3T
⇒ t = 40/3 years