You can put this solution on YOUR website!
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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.
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.
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
