If (20)² is subtracted from the square of a number, the answer so obtained is 4321. What is the number?	Choose the correct answer
A) 68 B) 69 C) 70 D) 71 E) 72

Rationale: x ^ 2 = 4321 + 400 = 4721 4761 = 69 * 69 x = 69 answer : b
Answer: B