The difference between C.I. and S.I. on an amount of $10,000 for 2 years is $49. What is the rate of interest per annum? Choose the correct choice from the following answers.
A) 5 %  B) 6 %  C) 7 %  D) 8 %  E) 9 %

Rationale: $ 49 is the interest on the first year of interest . let x be the interest rate . the interest after the first year is 10000 * x . the interest on the first year ' s interest is 10000 * x * x 10000 * x ^ 2 = 49 x = 0.07 the answer is c .
Answer: C