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January 31, 2015

January 31, 2015

Posted by **Janice - Please Help!!!** on Thursday, April 7, 2011 at 12:00pm.

- math -
**Mgraph**, Thursday, April 7, 2011 at 12:47pmWe find a from a system:

a +a+99d =7099.5

a+100d+a+199d=20799

We subtract from the 2nd the 1st:

200d=13699.5

d=68.4975

2a+99x68.4975=7099.5

a=159.12375 (0.12375=99/800)

- math -
**Steve**, Thursday, September 22, 2011 at 12:42pmUmmm.

Sn = n(a1 + an)/2

S100 = 100(a1 + a100)/2

= 50(a+a+99d)

= 100a + 4950

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