The difference between compound interest and simple interest on a certain amount of money at 5% per annum for 2 years is 18. Find the sum :  Options:	A) 4500	B) 7500	C) 5000	D) 7200	E) none of these

Rationale: "sol . ( d ) let the sum be 100 . therefore , si = 100 × 5 × 2100 = 10100 × 5 × 2100 = 10 and ci = 100 ( 1 + 5100 ) 2 − 100100 ( 1 + 5100 ) 2 − 100 ∴ = 100 × 21 × 2120 × 20 − 100 = 414 = 100 × 21 × 2120 × 20 − 100 = 414 difference of ci and si = 41 ⁄ 4 - 10 = 1 ⁄ 4 if the difference is 1 ⁄ 4 , the sum = 100 = > if the difference is 18 , the sum = 400 × 18 = 7200 answer d"
Answer: D