Question
Suresh earned an interest of Rs. 903 on principal amount
of Rs. 2800 at some rate of compound interest in 2 years. How much more/less interest would he have earned on Rs. 3200 at the same rate of simple interest for the same duration?Solution
Let, rate of interest be ‘r’% per annum So, 903 = 2800 × {(1 + r/100)2 – 1} 129/400 = {(1 + r/100)2 – 1} 529/400 = (1 + r/100)2 (23/20)2 = (1 + r/100)2 23/20 = 1 + r/100 3/20 = r/100, r = 15 So, simple interest earned = 3200 × 0.15 × 2 = Rs. 960 Required amount = 960 – 903 = Rs. 57
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