# Simple Interest - Aptitude Questions and Answers - RejinpaulPlacement

43.
If a sum of money at simple interest doubles in 6 years, it will become 4 times in:

Solution:   Let sum = x. Then, S.I. = x.
Rate = (100 * x)/(x * 6) = (50/3) %

Now, sum = x, S.I. = 3x, Rate = (50/3)%

Time = [100 * 3x]/[x * (50/3)] = 18 years.
44.
A sum of money trebles itself in 15 years 6 months. In how many years would it double itself?
Answer: b) 7 years 9 months

Solution:   Let sum = x. Then, S.I = 2x, Time = 15   1/2 years = 31/2 years.
Rate = [100 * 2x]/[x * (31/2)] = (400/31)%

Now, sum = x, S.I = x, rate = (400/31)%

Time = [100 * x]/[x * (400/31)] = 31/4 years = 7 years 9 months
45.
The simple interest on a sum of money at 8% per annum for 6 years is half the sum. The sum is:

Solution:   Let sum = x. Then, S.I. = x/2.
x/2 = (x * 8 * 6)/100.

46.
At what rate percent per annum will the simple interest on a sum of money be 2/5 of the amount in 10 years? [S.S.C. 2002]

Solution:   Let sum = x. Then, S.I. = 2x/5, Time = 10 years.

Rate = [(100 * 2x)/(x * 5 * 10)] % = 4%.
47.
In how much time would the simple interest on a certain sum be 0.125 times the principal at 10% per annum? [Assistant Grade, 1997]

Solution:   Let sum = x. Then, S.I = 0.125x = (1/8)x, R = 10%.

Time = [(100 * x)/(x * 8 * 10)] years = 5/4 = 1    1/4 years
48.
How long will it take a sum of money invested at 5% p.a. S.I. to increase its value by 40%?