Arithmetic Sequence Problem

[JamesD]

The sum of the first 42 terms is 3906. I need to find the 10th term and the sum of the first 20 terms. The difference between the terms is 4.

Can someone please help me with this one?

 

[JamesD]

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[stapel]

The sum of the first 42 terms is 3906. I need to find the 10th term and the sum of the first 20 terms. The difference between the terms is 4.

What formula did they give you for the sum of a geometric series? Given that you have the value of the sum, the value of "d", and the value of "n", what did you get? Where are you stuck?

Please be complete. Thank you!

 

[TchrWill]

The sum of the first 42 terms is 3906. I need to find the 10th term and the sum of the first 20 terms. The difference between the terms is 4.

Can someone please help me with this one?

I somehow feel that you already have the formulas for arithmetic series. If not, Denis has given you the site that will surely help you.

Given a series with "n" terms, with difference between terms of "d", first term of "a" and last term "l", and a sum of "n" terms equal to S,

you have
a, (a+d), (a+2d), (a+3d), ...
l = a + (n-1)d
S = (n/2)(a + l)

You have been given a sum of S = 3906, a difference of d = 4 and the number of terms as "42"

Solve for l and a.

Use the appropriate formula to determine the n = 10 term and the sum of the first 20 terms.