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Find the sum of money if the difference between compound interest and simple interest for 2 years at the rate of 9% interest per annum is Rs. 129.60 |
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Answer» Let the sum of money be Rs. x. `:.` At the rate of 9% interest per annum the amount of Rs.x for 2 years `=Rs. (1+9/100)^(2)` `:.` The compound interet `=Rs. {x(1+9/100)^(2)-x}=Rs. X{(1+9/100)^(2)-1}` `=Rs. X{(1+9/100)^(2)-(10^(2))=Rs. X{(1+9/100+1)(1+9/100-1)}` `=Rs.x(2+9/100)xx9/100=Rs. x xx209/100xx+9/100` `=Rs. (1881x)/10000` Again at the rate of 9% interest per annum. the simple of interest of Rs. x for 2 years `=Rs. (x xx9xx2)/100` `=Rs. (9x)/50` As per question `(1881x)/10000-(9x)/50=129.60` `implies(1881x-1800x)/10000=129.60` `implies81x=1296000` `impliesx=1296000/81=16000` `:.`The required sum of money `=Rs. 16000` |
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