A certain sum of money become 2.56 times of itself in 2 years at compound interest. Find the rate of interest if compounded annually.

60%

A = P( 1 + \(\frac{R}{100}\))^t                   

2.56 P = P ( 1 + \(\frac{R}{100}\))²            

 (1.6)² = ( 1 + \(\frac{R}{100}\))²

1.6 - 1 = \(\frac{R}{100}\) ⇒ 0.6 = \(\frac{R}{100}\)

R = 60%