## 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) 2800B) 2100C) 2400D) 1200Ans. DLet as take amout as x,(3600-x)x*5*4/100 +(3600-x)*5*6/100=960By 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 monthlike for 1st 12700-4000=87002nd 8700-3000=57003rd 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%

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