The compound interest on a certain sum of money for 2 year at the rate of 5% p.a. is Rs. 328. Find double of principal.

4000 4800 6400 3500

6400

5% = \(\frac{1}{20}\) Therefore, Let principal is 400   (square of 20) Total C. I.  = 41  ATQ, 41 R = 328  ⇒ 1R = 8 400 R = 400 × 8 = 3200 Double of principal = 3200 × 2 = Rs.6400