A certain sum becomes four times itself at simple interest in eight years. In how many years does it become ten times itself?
Answers: A) 24 years B) 14 years C) 65 years D) 17 years E) 15 years
Let the sum be Rs. x, then it becomes Rs. 4x in eight years Rs. 3x is the interest on x for eight years.   R = (100 * 3x)/(x * 8)   = 300/8 %   If the sum becomes ten times itself, then interest is 9x.   The required time period   = (100 * 9x)/(x * 300/8)   = (100 * 9x * 8)/(x * 300)   = 24 years.   Answer:15 years
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A certain sum becomes four times itself at simple interest in eight years. In how many years does it become ten times itself?