A certain sum earns simple interest of Rs. 800 in 2 years at a certain rate of interest. If the same sum earns compound interest of Rs.900in the same period of 2 years, What must be the rate of interest? Choose the most appropriate option.
A) 25%  B) 10%  C) 15%  D) 20%  E) 30%
Explanation:   Given: 800 = (P * R * 2) / 100   S.I. For 1 year = Rs. 400   Thus, (900 – 800) = S.I. on Rs. 400 for 1 year   100 = (400 * R * 1) / 100   R = 25% p.a.   25%NSWER: 25%
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A certain sum earns simple interest of Rs. 800 in 2 years at a certain rate of interest. If the same sum earns compound interest of Rs.900in the same period of 2 years, What must be the rate of interest?