# Simple Interest - Aptitude Questions and Answers - RejinpaulPlacement

29.
The interest on a certain deposit at 4.5% p.a. is Rs. 202.50 in one year. How much will the additional interest in one year be on the same deposit at 5% p.a.?
Solution:   S.I. = Rs. 202.50, R = 4.5% , T = 1 year.
Principal = Rs. (100 * 202.50)/(4.5 * 1) = Rs. 4500

Now, P = Rs. 4500, R = 5%, T = 1 year.
S.I. = Rs. (4500 * 5 * 1)/100 = Rs. 225

Difference in interest = Rs. (225 - 202.50) = Rs. 22.50
30.
A sum invested at 5% simple interest per annum grows to Rs. 504 in 4 years. The same amount at 10% simple interest per annum in 2   1/2 years will grow to: [C.D.S 2003]

Solution:   Let the sum be Rs. x. Then, S.I. = Rs. (504 - x).

(x * 5 * 4)/100 = 504 - x
=> 20x = 50400 - 100x
=> 120x = 50400
=> x = 420

Now, P = Rs. 420, R = 10 %, T = 5/2 years.
S.I. = Rs. [[(420 * 10)/100] * (5/2)] = Rs. 105.

Amount = Rs. (420 + 105) = Rs. 525
31.
What will be the ratio of simple interest earned by certain amount at the same rate of interest for 6 years and that for 9 years? [Bank P.O. 1998]

Solution:   Let the principal be P and rate of interest be R%.

Required ratio = [(P * R * 6)/100]/[(P * R * 9)/100] = 6PR/9PR = 6/9 = 2 : 3
32.
Nitin borrowed some money at the rate of 6% p.a. for the first three years, 9% p.a. for the next five years and 13% p.a. for the period beyond eight years. If the total interest paid by him at the end of eleven years is Rs. 8160, how much money did he borrow? [Bank P.O 2000]

Solution:   Let the sum be Rs. x. Then,

[(x * 6 * 3)/100] + [(x * 9 *5)/100] + [(x * 13 * 3)/100] = 8160.
=> 18x + 45x + 39x = (8160 * 100)
=> 102x = 816000
=> x = 8000
33.
The simple interest on a sum of money will be Rs. 600 after 10 years. If the principal is trebled after 5 years, what will be the total interest at the end of the tenth year?

Solution:   Let the sum be Rs. x.

Now, S.I. = Rs. 600, T = 10 years.
Rate = (100 * 600)/(x * 10) = (6000/x) %

S.I. for first 5 years = Rs. (x * 5 * 6000)/(x * 100) = Rs. 300
S.I. for last 5 years = Rs. [3x * 5 * [6000/(x+100)]] = Rs. 900.

Total interest = Rs. 1200.
34.
The simple interest on Rs. 10 for 4 months at the rate of 3 paise per rupee per month is:

Solution:   S.I. = Rs. [10 * (3/100) * 4] = Rs. 1.20
35.
An automobile financier claims to be leading money at simple interest, but he includes the interest every six months for calculating the principal. If he is charging an interest of 10%, the effective rate of interest becomes: [N.I.F.T. 2000]