Question

Find the sum: $5+(-5)+5+(-5)+............$

If the number of terms is $40$.

Answer 1

Finding the required sum:

$5+(-5)+5+(-5)+.............$ for this series up to $40$ terms, it is clear that there are $20$ terms which are $+5$(Positive value) and $20$ terms which are $-5$ (Negative value).

And, it is clear that $-5$ is the additive inverse of $+5$.

Also, the sum of integer with its additive inverse is always $0$.

Hence, $5+(-5)+5+(-5)+............$ upto $40$ terms $=0$