# Simple Interest - Aptitude Questions and Answers - RejinpaulPlacement

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36.
A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is: [Section Officers' 2001]
Answer: c) Rs. 698

Solution:   S.I. for 1 year = Rs. (854 - 815) = Rs. 39.
S.I. for 3 years = Rs. (39 * 3) = Rs. 117

Principal = Rs. (815 - 117) = Rs. 698.
37.
A sum of money lent out at simple interest amounts to Rs. 720 after 2 years and to Rs. 1020 after a further period of 5 years. The sum is: [S.S.C. 2004]
Answer: b) Rs. 600

Solution:   S.I. for 5 years = Rs. (1020 - 720) = Rs. 330
S.I. for 2 years = Rs. [(300/5) * 2] = Rs. 120.

Principal = Rs. (720 - 120) = Rs. 600
38.
A sum of money amounts to Rs. 9800 after 5 years and Rs. 12005 after 8 years at the same rate of simple interest. The rate of interest per annum is: [S.S.C. 2003]

Solution:   S.I. for 3 years = Rs. (12005 - 9800) = Rs. 2205.
S.I. for 5 years = Rs. [(2205/3) * 5] = Rs. 3675.

Principal = Rs. (9800 - 3675) = Rs. 6125.

Hence, rate = (100 * 3675)/(6125 * 5) = 12%
39.
A certain sum of money at simple interest amounts to Rs. 1012 in 2   1/2 years and to Rs. 1067.20 in 4 years. The rate of interest per annum is:

Solution:   S.I. for 1 1/2 years = Rs. (1067.20 - 1012) = Rs. 55.20
S.I. for 2   1/2 years = Rs. [55.20 * (2/3) * (5/2)] = Rs. 92.

Principal = Rs. (1012 - 92) = Rs. 920.

Hence, rate = (100 * 92 * 2)/(920 * 5) = 4%.
40.
In how many years will a sum of money double itself at 12% per annum?
Answer: d) 8 years 4 months

Solution:   Let sum = x. Then, S.I. = x.

Time= [(100 * S.I)/(P * R)] = [(100 * x)/(x * 12)] years
= 8   1/3 years
= 8 years 4 months
41.
At what rate percent of simple interest will a sum of money double itself in 12 years? [S.S.C. 2000]
Answer: b) 8   1/3 %

Solution:   Let sum = x. Then, S.I. = x.

Rate = [(100 * S.I.)/(P * T)]
= (100 * x)/(x * 12)
= (25/3) % = 8   1/3%
42.
The rate at which a sum becomes four times of itself in 15 years at S.I. will be: