A sum was put a simple interest at a certain rate for 1 years. Had it been put at 6% higher rate, it would have fetched Rs. 30 more. The sum is:  Choose the correct choice:
A) s . 500  B) s . 600  C) s . 700  D) s . 800  E) s . 900

Rationale: "explanation : let the sub be rs . x and the initial rate be r % . then x ã — ( r + 6 ) ã — 1 / 100 â ˆ ’ x ã — r ã — 1 / 100 = 30 â ‡ ’ x ã — 6 ã — 1 / 100 = 30 â ‡ ’ x ã — 1 / 100 = 5 â ‡ ’ x = 500 answer : option a"
Answer: A