Question

What is the sum of a 28-term arithmetic sequence where the first term is 12 and the last term is 255?

Answer 1

Formula: Sn = n(a1 +an)/2

So,
\[S28= 28 ( 12 +255)/2\]

Simplify

Answer 2

3318

Answer 3

2,937
3,204
3,471
3,738

Answer 4

@TwinYang

Answer 5

You didn't simplify correctly, simplify again.

Answer 6

got the same thing

Answer 7

Simplify 12+255 to 267
x=28×267/2

2 Simplify 28×267 to 7476
x=7476/2

3 Simplify 7476/2 to 3738
x=3738

Answer 8

oh thank you!