How much of an alloy with 30% copper must be added to 25 pounds of a second alloy which is 20% copper to create a 27% alloy?

If is the amount (by weight) of the first alloy that you will use, then the new alloy will have a total weight of .

The second alloy has 5 pounds of copper (20% of 25 = 5). 30% of the first alloy is copper, so that the amount of copper being introduced is , making the total amount of copper in the new alloy .

We want the proportion of copper in the new alloy to come out to 27% of the new alloy's weight, so that

an advantage of the standard deviation is that it increases as the dispersion of the data increases. e. the interquartile range is preferred when the data are not skewed or no have outliers. an advantage of the standard deviation is that it uses all the observations in its computation.

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