# Easy series

1. Dec 12, 2011

### mtayab1994

1. The problem statement, all variables and given/known data

$$1+2+3...+n$$

2. Relevant equations

count the sum.

3. The attempt at a solution

it's such an easy sum to count but i just want to make sure.

$$S_{n}=\frac{n}{2}(a_{1}+a_{n})$$

$$S_{n}=\frac{n}{2}(1+n)$$

$$S_{n}=\frac{n+n^{2}}{2}$$

2. Dec 12, 2011

### Gengar

Correct. Hope your anxiety is eased

3. Dec 12, 2011

### mtayab1994

Lol its too simple idk why my teacher would give us something so simple I thought there would be a trick or something.