The difference between simple and compound interest (compounded-annually) on a sum of money for 2 years at 10% per annum is Rs 65. The sum is_________?

A. Rs 6500
B. Rs 6565
C. Rs 65065
D. Rs 65650
Explanation:
Let the sum be Rs x.
Then [x × (1 +10/100)2 – x] – (x × 10/100 × 2) = 65
=> (x × 11/10 × 11/10 – x) – x/5 = 65
=> (121x/100 – x) – x/5 = 65
=> (21x/100 – x/5) = 65
=> (21x – 20x) = 6500
=> X = 6500