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# SIMPLE INTEREST & COMPOUND INTEREST SET3

Q.1 If difference between C.I. & S.I. on a certain sum of money for 2yrs at 5% p.a. is Rs.122. Find the sum ?

A) Rs. 14000

B) Rs. 15000

C) Rs. 16000

D) Rs. 17000

Ans. C

Shortcut :

Sum = Difference * (100)3 / r2 (300+r)

Or 122 * (100)3 / 52 (300+5)

=Rs. 16000

Q.2 If C.I. on a certain sum for 2 yrs at 12% p.a. is Rs. 1590. What would be the S.I. ?

A) Rs. 1400

B) Rs. 1500

C) Rs. 1600

D) Rs. 1700

Ans. B

S.I. = R * t / 100 [1 + R/100]2 – 1 * C.I.

Or 12 * 2 / 100 [1 + 12/100]2 – 1 * 1590

Thus on solving we get,

Rs.1500

Q.3 Gopal lends Rs 3600 on simple interest to Hemant for a period of 5 years. He lends a part of the amount at 4% interest and the rest at 6% and receives Rs. 960 as the amount of interest. How much money did he lend on 4% interest rate?
A) 2800
B) 2100
C) 2400
D) 1200
Ans. D
Let as take amout as x,(3600-x)
x*5*4/100 +(3600-x)*5*6/100=960
By solving,
x=1200

Q.4 UPSC ONLINE ACADEMY wants to buy an air-conditioner for his office. He went to a shop and selects an AC whose price is Rs 12700. The shopkeeper gave him two offers either you pay the full amount of Rs 12700 or pay only Rs 4000 and installment of Rs 3000 per month for the next 3 months just paying Rs. 300 as interest. What is the rate of interest the shopkeeper charged from UPSCONLINE ?

A) 23

B) 22

C) 26

D) 21

Ans. D

To solve this we have to find a total principle of each month
like for 1st 12700-4000=8700
2nd 8700-3000=5700
3rd 5700-3000=2700

total principal =17100

so use normal formula to find r% per month and take time = 1/12(per month )
so r=300*100/17100*(1/12)= 21%