Question

done

Answer 1

@mathmale

Answer 2

If given the first and last terms of an arithmetic progression of n terms, then the sum of those n terms is given by\[S _{n}=\frac{ n }{ 2 }(t _{1}+t _{n})\]where\[t _{1}\]and\[t _{n}\]are the first and the last terms respectively.

Answer 3

so n stands for term number and I plug in the last term? and 1 equals the first term so like

sn= 1/2(10_1+3_75) I am so confused

Answer 4

NO, you are misinterpreting the formula. It is\[\frac{ n }{ 2 }(first term + last term)\]if you know the first and last terms. Understand?!

Answer 5

oh so n/2(3+75)

Answer 6

Yes, exactly. n is the # of terms.

Answer 7

Thus n = 10, for your problem.

Answer 8

So what is your final answer? @xoalybabyxo

Answer 9

390 right 5*78

Answer 10

Yes, 390.

Answer 11

thank you very much

Answer 12

Very welcome! Anytime!