Compound Interest Problems 2016

Hello and welcome to exampunditHere is a set of Quantitative Aptitude Quiz based on Compound Interest Problems. Now, these questions are from Basic to Moderate just to rectify your errors and brush up your skills.

1. Ruchi borrows Rs. 13040 at 3 ¾% per annum from a bank. Compound interest is to be repaid in two equal yearly instalments. Find the amount of each instalment.
(A) Rs. 6889
(B) Rs. 7259
(C) Rs. 8689
(D) Rs. 5124.50
(E) None of these
2. A sum of money placed at compound interest doubles itself in 4 years. In how many years will it amount to 8 times?
(A) 6 years
(B) 8 years
(C) 12 years
(D) 10 years
(E) None of these

3. Find the compound interest of Rs. 10,000 in 9 months at 4% per annum interest payable quarterly.
(A) Rs. 300
(B) Rs. 310
(C) Rs. 303
(D) Rs. 303·01
(E) None of these

4. Some money was lent on 4% C.I. If the difference in interest of second and the first year is Rs. 88, find out the sum.
(A) Rs. 50,000
(B) Rs. 60,000
(C) Rs. 65,000
(D) Rs. 55,000
(E) None of these

5. The population of a town is 50,000. It decreases by 20 per thousand per year. Find out the population after 2 years.
(A) 46,000
(B) 46,200
(C) 48,020
(D) 48,320
(E) None of these
6. If the population of a town at present is 10648 and the rate of increment is 10% per year. What was the population before 3 years?
(A) 10,000
(B) 9,000
(C) 11,000
(D) 8,000
(E) None of these
7. Akarsh left a will of Rs. 16,400 for his two sons aged 17 and 18 years. They must get equal amounts when they are 20 years at 5% compound interest. Find the present share of the younger son.
(A) Rs. 8,000
(B) Rs. 8,400
(C) Rs. 8,200
(D) Rs. 10,000
(E) None of these
8. The compound interest on a sum of money for 2 years is Rs. 410 and the simple interest on the same sum for the same period and at the same rate is Rs. 400. Find the rate of interest.
(A) 4%
(B) 3%
(C) 5%
(D) 6%
(E) None of these

Solutions by Arjit:

(1) Installment* [(100/100+r)+(100/100+r)^2=Borrowed Amount

Use this formula to get Answer

(2) 4 years me 2 times

4+4 yrs me 4 times

4+4+4 yrs me 8 times

(3) Interest=10000(1+1/100)^3-10000

(4) First year CI or SI will be same=4 Rs

Second year interest=100[(1+4/100)^2)-100=4.16

Difference=4.16-4.00=0.16

……0.16———100

1—————100/0.16

88…………100*88/0.16=55000

(5) 50000(1-20/1000)^2……Please note, it is mentioned 1000 here.

(6)10648=P(1+10/100)^3…CALCULATE P

(7) Let share be x and 16400-x…..x elder and 16400-x younger

x(1+5/100)^2=16400-x(1+5/100)^3

because 18 yrs son will become 20 yrs in 2 yrs and 17 years son will become in 3 yrs

(8) Difference in CI-SI = 410 – 400 = Rs. 10

SI 1 year = 400/2 = Rs. 200 ..

This will work as Pricpl for next yr and intrest will be 10 rupees

10=200*r*1/100

r= 5%

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