Find the total sum of all integers from 21 to 50, inclusive.

Step-by-step solution

1. Recognise it as an arithmetic series: $a=21$, $l=50$, $n=50-21+1=30$ terms.
2. Apply $S=\frac{n}{2}(a+l)$.
3. Calculate $n/2=15$ and $a+l=71$.
4. Multiply: $15\times 71=1065$.
5. Result is $1065$.

Concept tested: Arithmetic series sum

Published 1 October 2026 · How this solution was prepared and checked