Multiple choice

A sum of Rs. 12,800 is invested partly at 15% per annum and the remaining at 12% per annum simple interest. If the total interest at the end of 3 years is Rs. 5,085, then how much money was invested at 15% per annum?

  1. Rs. 5,200

  2. Rs. 7,500

  3. Rs. 5,800

  4. Rs. 5,300
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let x be the amount at 15% and (12800 - x) be the amount at 12%. The total interest is given by (x * 0.15 * 3) + ((12800 - x) * 0.12 * 3) = 5085. Solving this linear equation: 0.45x + 4608 - 0.36x = 5085, which simplifies to 0.09x = 477, so x = 5300.

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