  # Simple Interest - Aptitude Questions and Answers - RejinpaulPlacement 1.
Find the simple interest on Rs. 68,000 at 16    2/3% per annum for 9 months.

Solution:   P = Rs. 68000, R = 50/3 %p.a and T = 9/12 years = 3/4 years

S.I = (P * R * T)/100
= Rs. [68000 * (50/3) * (3/4) * (1/100)]
= Rs. 8500. 2.
Find the simple interest on Rs. 3000 at 6   1/4 % per annum for the period from 4th Feb., 2005 to 18th April, 2005.

Solution:   Time = (24 + 31 + 18) days = 73 days = 73/365 year = 1/5 year.
P = Rs. 3000
R = 6   1/4 % p.a. = 25/4 % p.a.

S.I = Rs. [3000 * (25/4) * (1/5) * (1/100)] = Rs. 37.50

[Remark: The day on which money is deposited is not counted while the day on which money is withdrawn is counted] 3.
A sum at simple interest at 13   1/2 % per annum amounts to Rs. 2502.50 after 4 years. Find the sum.

Solution:   Let sum be Rs. x.
Then, S.I = Rs. [x * (27/2) * 4 * (1/100)] = Rs. 27x/50.

Amount = Rs. [x + (27x/50)] = Rs. 77x/50.

77x/50 = 250250
=> x = (250250 * 50)/77 = 1625.

Hence, sum = Rs. 1625 4.
A sum of Rs. 800 amounts to Rs. 920 in 3 years at simple interest. If the interest rate is increased by 3%, it would amount to how much?

Solution:   S.I = Rs. (920 - 800) = Rs. 120; P = Rs. 800; T = 3 yrs.

R = [(100 * 120)/(800 * 3)] % = 5 %.

New rate = (5 + 3) % = 8 %.

New S.I = Rs. (800 * 8 * 3)/100 = Rs. 192.

New amount = Rs. (800 + 192) = Rs. 992 5.
Adam borrowed some money at the rate of 6 % p.a. for the first two years, at the rate of 9 % p.a. for the next three years, and at the rate of 14 % p.a. for the period beyond five years. If he pays a total interest of Rs. 11,400 at the end of nine years, how much money did he borrow? [Bank P.O. 1999]

Solution:   Let the sum borrowed be x. Then,
[(x * 6 * 2)/100] + [(x * 9 * 3)/100] + [(x * 14 * 4)/100] = 11400.
=> [(3x/25) + (27x/100) + (14x/25)] = 11400
=> 95x/100 = 11400
=> x = (11400 * 100)/95 = 12000.

Hence, sum borrowed = Rs. 12,000 6.
A certain sum of money amounts to Rs. 1008 in 2 years and to Rs. 1164 in 3   1/2 years. Find the sum and the rate of interest.

Solution:   S.I for 1 1/2 years = Rs. (1164 - 1008) = Rs. 156
S.I for 2 years = Rs. [156 * (2/3) * 2) = Rs. 208

Principal = Rs. (1008 - 208) = Rs. 800.

Now, P = 800, T = 2 and S.I = 208.

Rate = [(100 * 208)/(800 * 2)] % = 13 % 7.
At what rate percent per annum will a sum of money double in 16 years? [R.R.B. 2003] 