# Math

posted by .

how many terms of the arithmetic sequence -5,-1,3,… must be added to reach the sum of 400

• Math -

a = -5
d = 4

So,

n/2 (-10+4(n-1)) = 400
n = 16

## Similar Questions

1. ### Math

1. What are the next two terms of the following sequence?
2. ### Precalculas

The sum of the first 30 terms of one arithmetic sequence is 300 more than the sum of the first 30 terms of another arithmetic sequence. what could the  sequences be?
3. ### Can someone help me?!

The 1st, 5th and 13th terms of an arithmetic sequence are the first three terms of a geometric sequence with a common ratio 2. If the 21st term of the arithmetic sequence is 72, calculate the sum of the first 10 terms of the geometric …
4. ### 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 …
5. ### Arithmetic Sequence Help!

The sum of 3 consecutive terms of an arithmetic sequence is 165. The second of these terms is 11 times the first. Find the 3 terms From what I gathered: S(3) = 165 t(2)= 11(t1) The given formulas are: Sn= n/2[2a+(n-1)d] and tn=a+(n-1)d …
6. ### Mathematics arithmetic sequence

The sum of second and sixth terms of an arithmetic sequence is 4. The third term is 24 more than eleventh term. So determine the first three terms of the sequence.
7. ### 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 …
8. ### math

The 1st,5th,13th term of an arithmetic sequence are the first 3 terms of geometric sequence with a common ratio of 2. If the 21st term of the arithmetic sequence is 72, calculate the sum of the first 10 terms of the geometric sequence.
9. ### 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
10. ### Arithmetic sequence

Three consecutive terms of an arithmetic sequence have a sum of 12 and a product of -80 .Find the terms. [hint : let the terms be x - d, x and x + d . ]

More Similar Questions