Review question

# When does $1-2+3-4+5-\cdots +(-1)^{n+1}n$ reach $100$? Add to your resource collection Remove from your resource collection Add notes to this resource View your notes for this resource

Ref: R8998

## Suggestion

The smallest possible integer $n$ such that $1-2+3-4+5-6+\cdots +(-1)^{n+1}n \geq 100$ is

1. $99$,

2. $101$,

3. $199$,

4. $300$.

What is the sum of the terms of the sequence when $n=1$?

What about when $n=2$? $n=3$? $n=4$?

When will this sum reach $100$?

Or… what is the sum of the first $2n$ terms of the sequence?