A sum of Rs. 5324 is accumulated in 3 years at 10% compound interest, What is the original amount = ?

Answer: Option B

Let the principal = 1000, r = 10%, T = 3Year
Rate r = 10% = $$\frac{1}{10}$$

Amount = 300 + 30 + 1 + 1000(Principal) = 1331
⇒1331 unit → 5324
⇒ 1unit → $$\frac{5324}{1331}$$
∴ 1000unit = $$1000\times \frac{5324}{1331}$$     = 4000