8. The pages of a report are numbered consecutively from 1 to 10. If the sum of the page numbers up to and including page number x of the report is equal to one more than the sum of the page numbers following page number x, then x =

(A) 4 (B) 5 (C) 6 (D) 7 (E) 8

Numbering from 1-10
It means (1+2+3....+x)-(x+1+x+2...10)=1
I arrived at the answer by mere substitution...

1)If x = 4
Then sum of (1+2+3+4) =10<(5+6+7+8+9+10)
Hence incorrect
2)If x = 5
Then sum of (1+2+3+4+5)<(6+7+8+9+10)
3) If x = 6
Then sum of (1+2+3+4+5+6)<(7+8+9+10)
4) If x = 7
then sum of (1+2+3+4+5+6+7) = 28 and sum of (8+9+10)=27
28-27 = 1
Hence correct

This can be simplified by an easier way using the AP formula.