Question

8. What is the sum of the arithmetic sequence 140, 136, 132..., if there are 35 terms?

Answer 1

Can you tell me what the last term is?

Answer 2

They dont say. I have to figure it out I guess.

Answer 3

Do you know how to figure out the last term?

Answer 4

No clue:/

Answer 5

the general term is

an = a1 + d(n-1)

The first term is 140, the common difference is -4, so a1 = 140 and d = -4

Answer 6

therefore we can say

an = 140 + (-4)(n-1)

Now we want the 35th term of this sequence, so plug in n = 35

an = 140 + (-4)(35-1)

an = 140 + (-4)(34)

an = 140 - 136

an = 4

Answer 7

so the last term (the 35th term) is 4

Answer 8

so..

Sum of first 35 terms

S = (n*(a1 + an))/2

S = (35*(140 + 4))/2

S = ???

Answer 9

2,520!?

Answer 10

yep, you nailed it