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December 18, 2014

December 18, 2014

Posted by **Poppy** on Sunday, December 18, 2011 at 7:34pm.

s=n(2a+(n-1)d)/2

- math -
**Reiny**, Sunday, December 18, 2011 at 8:03pma+8d = 23

a+32d = -241

subtract them ...

24d = -264

d = -11

back into the first ....

a - 88 = 23

a = 111

now that we know a = 111, d = -11 and n = 15

just plug those values into your formula

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