A certain sum amounts to Rs. 81840 in 3 years and to Rs. 92400 in 5 years at x% p.a. under simple interest. If the rate of interest is becomes (x+2)%, then in how many years will the same sum double itself?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 10.
Let the initial principal be P.
P + SI of 3 years = 81840....(1)
P + SI for 5 years = 92400.....(2)
Subtract eq(1) from (2) we get,
SI for 2 years = 10560
SI for 1 year = 5280.
SI for 3 years = 5280 × 3 = 15840.
P = 81840 - 15840 = 66000
Rate of interest = (5280/66000) × 100 = 8%.
x = 8%
x + 2 = 10%
In 10 years the sum of 66000 becomes 132000.