The sum of the even numbers between 1 and n is 89*90, where n is an odd number, then n=?	Choose the correct choice.
A) 167 B) 173 C) 179 D) 185 E) 193

Rationale: "let n - 1 = 2 a . 2 + 4 + . . . + 2 a = 2 * ( 1 + 2 + . . . + a ) = 2 * ( a ) ( a + 1 ) / 2 = ( a ) ( a + 1 ) = 89 * 90 then a = 89 and n = 179 . the answer is c ."
Answer: C