Multiple choice

A sum on compound interest amounts to Rs.77440 in 2 years and Rs.85184 in 3 years.Find the sum.

  1. Rs.64000

  2. Rs.68000

  3. Rs.72000

  4. Rs.68400
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A Correct answer
Explanation

In compound interest, amount after n years is P(1 + r)^n. A3/A2 = (1+r), so 1+r = 85184/77440 = 1.0992... ≈ 1.1. Thus r = 10%. Principal P = 77440/(1.1)^2 = 77440/1.21 = 64000. Verify: Year 2 = 64000 × 1.21 = 77440, Year 3 = 64000 × 1.331 = 85184. Correct.

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