SOLUTION: How many terms ofthe sequence -24, -15, -6, and 3 will give a sum of 1230?

Question 1041613: How many terms ofthe sequence -24, -15, -6, and 3 will give a sum of 1230?

Found 3 solutions by Fombitz, ikleyn, MathTherapy:
Answer by Fombitz(32388)   (Show Source): You can put this solution on YOUR website!

,
,
,
On the face of it, you're adding a bunch of negative numbers (if the difference between the two numbers is 9, then 3 is the only positive number) to get a large positive sum.
Something is wrong with your problem setup.
Please check it and repost with a corrected question.

Answer by ikleyn(52790)   (Show Source): You can put this solution on YOUR website!
.
How many terms of the sequence -24, -15, -6, and 3 will give a sum of 1230?
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It is an arithmetic progression, first term is -24, the common difference is 9. The sum of the first n terms is equal to = (see the lesson Arithmetic progressions in this site). Or = . Solve this equation for n and get the answer.

Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

How many terms ofthe sequence -24, -15, -6, and 3 will give a sum of 1230?

Use the formula for the SUM of an AP: , where:
= First term in AP (- 24 in this case)
= Sum of n terms (1,230 in this case)
= number of terms in the AP (unknown)
= Common difference (9 in this case)
Thus, becomes:

Continue to solve for n (the number of terms). You should get
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