The sum of the even numbers between 1 and k is 79*80, where k is an odd number, then k=	Choose the correct choice from the following options
A) 79  B) 80  C) 81  D) 157  E) 159
The number of terms in this set would be: n=(k-1)/2 (as k is odd)   Last term: k-1   Average would be first term+last term/2=(2+k-1)/2=(k+1)/2   Also average: sum/number of terms=79*80/((k-1)/2)=158*80/(k-1)   (k+1)/2=158*80/(k-1) --&gt; (k-1)(k+1)=158*160 --&gt; k=159   Answer 159.
<result>E</result>
The sum of the even numbers between 1 and k is 79*80, where k is an odd number, then k=