If X is invested in a bank at a rate of simple interest of y% p.a. for two years, then the interest earned is 900. if X is invested at y% p.a., for two years when the interest is compounded annually, the interest is 922.50. What is the value of X?  Choose the correct choice.
A) 9000 B) 6000 C) 5000 D) 4000 E) 3000

Rationale: simple way to solve this question is to use options . from si , we know that x * y = 45,000 . now , put the value of x = 9000 , we will have y = 5 % to calculate ci , now , we know 1 st year amount = 9000 + 5 % of 9000 = 9450 . 2 nd year , amount = 9450 + 5 % of 9450 = 9922.50 . we can see after 2 years interest = 9922.50 - 9000 = 922.50 . hence , it satisfies the question . hence a is the correct answer
Answer: A