The sum of the even numbers between 1 and n is 95*96, where n is an odd number, then n=?
Select
A) 167 B) 175 C) 183 D) 191 E) 199

Rationale: "let n - 1 = 2 a . 2 + 4 + . . . + 2 a = 2 * ( 1 + 2 + . . . + a ) = 2 * ( a ) ( a + 1 ) / 2 = ( a ) ( a + 1 ) = 95 * 96 then a = 95 and n = 191 . the answer is d ."
Answer: D