The sum of the even numbers between 1 and n is 81*82, where n is an odd number, then n=?
Choose the correct choice from the following choices
A) 163 B) 171 C) 177 D) 185 E) 193
Let n-1 = 2a.   2+4+...+2a = 2*(1+2+...+a) = 2*(a)(a+1)/2 = (a)(a+1) = 81*82   Then a = 81 and n = 163.   The answer is 163.
<result>A</result>
The sum of the even numbers between 1 and n is 81*82, where n is an odd number, then n=?