# How to compute a weighted average?

4 transactions take 10 days each to complete 2 transactions take 8 days each to complete 9 transactions take 11 days each to complete 1 transaction takes 40 days to complete

How does one compute the weighted average time to complete a transaction?

Thanks!

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Well how do you wanna weight the average? What did you try? –  Dominic Michaelis Mar 14 '13 at 21:21

Just average together the list [10, 10, 10, 10, 8, 8, 11, 11, 11, 11, 11, 11, 11, 11, 11, 40].

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$$\frac{4*10 + 2*8 + 9*11 + 1*40}{4 + 2 + 9 + 1}$$