Answer
$\sum_{i=1}^{40} i$
Work Step by Step
In order to set up the summation notation, we must calculate the value which keeps constantly changing. That value will be designated as the $i$ term . The remaining terms that are the same would remain the same or constant in the summation notation.
Thus, we get the summation notation such as: $\sum_{i=1}^{40} i$
