# Compound Interest - Aptitude Questions and Answers - RejinpaulPlacement

15.
What annual payment will discharge a debt of Rs. 7620 due in 3 years at 16   2/3% per annum compound interest?

Solution:   Let each instalment be Rs. x. Then,

(P.W. of Rs. x due 1 year hence) + (P.W. of Rs. x due 2 years hence) + (P.W. of Rs. x due 3 years hence) = 7620

x/[1 + [50/(3 * 100)]] + x/[1 + [50/(3 * 100)]]^2 + x/[1 + [50/(3 * 100)]]^3 = 7620
=> (6x/7) + (36x/49) + (216x/343) = 7620
=> 294x + 252x + 216x = 7620 * 343
=> x = [(7620 * 343)/762] = 3430

Amount of each instalment = Rs. 3430
16.
Albert invested an amount of Rs. 8000 in a fixed deposit scheme for 2 years at compound interest rate 5 p.c.p.a. How much amount will Albert get on maturity of the fixed deposit? [Bank P.O. 1999]

Solution:   Amount = Rs. [8000 * [1 + (5/100)]^2 ]
= Rs. [8000 * (21/20) * (21.20)]
= Rs. 8820
So, the correct answer is (d)
17.
What will be the compound interest on a sum of Rs. 25,000 after 3 years at the rate of 12 p.c.p.a.? [S.B.I.P.O. 2003]

Solution:   Amount = Rs. [25000 * [1 + (12/100)]^3 ]
= Rs. [25000 * (28/25) * (28/25) * (28/25)]
= Rs. 35123.20

C.I. = Rs. (35123 - 25000) = Rs. 10123.20
18.
The compound interest on Rs. 20,480 at 6   1/4% per annum for 2 years 73 days, is :

Solution:   Time = 2   73/365 years = 2    1/5 years

Amount = Rs. [20480 * [1 + [25/(4 * 100)]]^2 [1 + [[(1/5) * (25/4)]/100]]]
= Rs. [20480 * (17/16) * (17/16) * (81/80)] = Rs. 23409

C.I. = Rs.(23409 - 20480) = Rs. 2929
19.
A man saves Rs. 200 at the end of each year and lends the money at 5% compound interest. How much will it become at the end of 3 years? [Hotel Management, 2003]

Solution:   Amount = {200 [1 + (5/100)]^3} + {200[1 + (5/100)]^2} + {200[1 + (5/100]}
= Rs. [200 * (21/20) * (21/20) * (21/20) + 200 * (21/20) * (21/20) + 200 * (21/20)]
= Rs. [200 * (21/20){(21/20) * (21/20) + (21/20) + 1}]
= Rs. 662.02
20.
Sam invested Rs. 15,000 @ 10% per annum for one year. If the interest is compounded half-yearly, then the amount received by Sam at the end of the year will be: [S.B.I.P.O. 2002]

Solution:   P = Rs. 15000; R = 10% p.a. = 5% per half-year; T = 1 year = 2 half-year.

Amount = Rs. [15000 * [1 + (5/100)]^2 ]
= Rs. [15000 * (21/20) * (21/20)]
= Rs. 16537.50.
21.
A bank offers 5% compound interest calculated on half-yearly basis. A customer deposits Rs. 1600 each on 1st January and 1st July of a year. At the end of the year, the amount he would have gained by way of interest is: [N.D.A. 2000]