Question

A sum invested at compound interest amounts to Rs. 3,136 in two years and Rs. 3,512.32 in 3 years at a certain rate percentage per annum, when the interest is compounded annually. What will the same sum amount to at the same rate in 8/3 years, interest compounded annually (nearest to one rupee)?
1. Rs. 3,387
2. Rs. 3,378
3. Rs. 3,487
4. Rs. 3,478

Answer 1

Correct Answer - Option 1 : Rs. 3,387

Given:

Amount (A₁) = Rs.3136

Time = 2years

Amount (A₂) = Rs.3512.32

Time = 3 years

By using Ratio method

Rate = 12% = 3/25

25               ∶          28

25               ∶          28

25               ∶          27                       (for 3^rd year = (3/25) × (2/3) = 2/25)

15625        ∶         21168

Now,

15625 = 2500

1 = 2500/15625

1 = 0.16

21168 = 0.16 × 21168

⇒ 3386.88

≈ 3387

∴ The New amount will be Rs.3387