Posted by **BEANAGEE** on Thursday, December 21, 2006 at 6:14pm.

the sum of the first n terms of an arithmetic series is -51. the series has a constant difference of -1.5 and a first term of four. Find the number of terms in the sum

I find using an EXCEL spreadsheet is very helpful for these types of problems. Start with 4 and keep adding 1.5. Then sum the series ending at each of the values. I get n=12

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