## anonymous 3 years ago how do you find the sum of a list of numbers.... ex.... 8,16,....312,320

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1. anonymous

I know you have to find the average and multiply with the count or somthing like that

2. anonymous

This is an ARITHMETIC series: It goes up by a constant number. To sum this, first figure out how many terms there are in the series. Let the terms be denoted as such: T1 = 8 T2 = 16 ... Tn = 8n. So if Tn = 320 = 8n then n = 40. Therefore you have 40 terms. Now to sum the series you multiply the number of terms by the average of the first and last terms. Then divide by 2. $\frac{40(8+320)}2=6560$

3. anonymous

I can explain why this works if you like