HE SUM OF EVEN INTEGERS:
The sum of the even numbers between 1 and k is 79*80, where k is an odd number, then k=? Choices.
A) 79
B) 80
C) 81
D) 157
E) 159
(E) 159   sum of numbers till n = n(n+1)/2 , sum of even numbers will be almost half of this i.e. n(n+1)/4 .   so if S = 79.80, then n= 159.
<result>E</result>
HE SUM OF EVEN INTEGERS:
The sum of the even numbers between 1 and k is 79*80, where k is an odd number, then k=?