# math

posted by .

Find the sum of the first 33 terms of the arithmetic sequence whose first term is 3 and whose 33rd term is -253

• math -

As you (should) know,

Sn = n/2 (a1 + an)
S33 = 33/2 (a1 + a33)
= 33/2 (3 - 253)
= 33/2 (-250)
= -33*125 = -4125

## Similar Questions

1. ### arithmetic

Find the sum of the first 25 terms of an arithmetic sequence whose 7th term is −247 and whose 18th term is −49.
2. ### Maths

1..The first 2 terms of a geometric progression are the same as the first two terms of an arithmetic progression.The first term is 12 and is greater than the second term.The sum of the first 3 terms od the arithmetic progression is …
3. ### Algebra1

Find the sum of the first 33 terms of the arithmetic sequence whose first term is 3 and whose 33rd term is -253.
4. ### Math

Solve for the 1st term of the arithmetic sequence whose 33rd term is -2p and whose 61st term is 26p.
5. ### math

Find the sum of the first 60 terms of the arithmetic sequence whose first term is −15 and whose common difference is 7.
6. ### math

in an arithmetic sequence the common difference is equal to 2.the first term is also the first term of a geometric sequence. the sum of the first 3 terms of an arithmetic sequence and the sum of the first 9 terms of an arithmetic sequence …
7. ### math

in an arithmetic sequence whose first term is 4, the 1st, 3rd and 7th terms form consecutive terms of geometric sequence, find the sum of the first three terms of the arithmetic sequence
8. ### Quick math help

Find the tenth term of the sequence: -6,1,8... Is it 57?
9. ### Quick Math Help

Find the tenth term of the sequence: -6,1,8... Is it 57?
10. ### Quick math help

Find the tenth term of the sequence: -6,1,8... Is it 57?

More Similar Questions