Discussion of Question with ID = 089 under Simple-Interest

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Question

A sum of Rs. 1300 is split into two parts. The first part is invested at 12% p.a. and the second at 4% p.a. What is the amount invested at 12% if the total simple interest at the end of 4 years is Rs. 368?

A

Rs. 500.

B

Rs. 600.

C

Rs. 400.

D

Rs. 700.

Soln.
Ans: a

Let the amount x be invested at r1% and remaining (P - x) at r2%, and let the sum of interests be I. Then, I = ${x × r_1 × 4}/100$ + ${(P - x) × r_2 × 4}/100$, which simplifies to 100I = 4 × ($x × (r_1 - r_2) + P × r_2$). Putting r1 = 12, r2 = 4, P = 1300, I = 368, we get x = Rs. 500.

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