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Asum of money lends at compound interest. if compound interest at the end of 2nd year and at the end of fourth year are rs 1980 and rs.4831.20. find the compound interest earned in 3rd year? |
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Answer» -step explanation: A sum of money is accumulating at compound interest at a CERTAIN rate of interest. If simple interest instead of compound were reckoned, the interest for the first two years would be diminished by Rs. 20 and that for the first three years by Rs. 61. Find the sum. A) Rs.7000 B) Rs.8000 C) Rs.7500 D) Rs.6500 Correct Answer: B) Rs.8000 Description for Correct answer: Let the principal be P and rate of interest be r %. Then, principal (i) when difference between C.I. and S.I is for 2 yr) is GIVEN by P = 20×(100)2r2 (ii) When difference between CI & SI in for 3 yrs in given by P = 61×(10)6r2(300+r) From eqs. (i) and (ii), 20×104r2 = 61×108r2(300+r) => r = 305 - 300 = 5 % From eq.(i), P = 20×10425 = Rs.8000 |
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