Sum of Integers in an Interval (for odd # of integers)

GRE Quant Problem Solving
1

I’m having trouble understanding whether the steps for finding the sum of integers in an interval (where first =/= 1) works in the situation where the total # integers in the interval is odd. These are the steps I’m referring to:

  1. Find the total number of integers in the interval
  2. Sum the first and last integers in the interval
  3. Multiple the values from #1 and #2 together and divide by 2.

The reason I’m having trouble understanding this is because I don’t have any practice problems and solutions to check whether this also works in those scenarios. The ones give in prepswift in the lesson exercise quiz and tickbox quiz are either for 1-n scenarios or even # of integers in interval scenarios.

2

Try making an example yourself.