If the sum of 1st n integers is 55 then what is n?	Choose the correct choice from the following.
A) 5 B) 7 C) 8 D) 10 E) 9
10escription :   sum=n(n+1)/2   sum=55   n^2+n=55*2   n^2+n-110=0   (n-10)(n+11)=0   n=10,-11,neglect negative ans   answer =10   Answer 10
<result>D</result>
If the sum of 1st n integers is 55 then what is n?