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Given the ratio of copper to zinc in brass, calculate how much more copper than zinc is used to create a given amount of brass.

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Used for chemistry/materials

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Brass is made from copper and zinc in the ratio  {girlsratio} : {boysratio}

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Imagine the elements in piles, before they are combined into the alloy.
There are {girlsratio} piles of copper and {boysratio} piles of zinc, therefore {boysratio + girlsratio} piles altogether.

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Each pile will therefore weigh:

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{classsize}g ÷ {boysratio + girlsratio} = {scalefactor}g.

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Zinc:
{boysratio} x {scalefactor} = {scalefactor*boysratio}g, as there are {boysratio} piles of zinc.

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Copper:
There are {girlsratio} x {scalefactor} = {scalefactor*girlsratio}g, as there are {girlsratio} piles of copper.

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However, we need to find how much more copper than zinc.

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{scalefactor*girlsratio} - {scalefactor*boysratio} = {scalefactor*girlsratio - scalefactor*boysratio}

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There is {scalefactor*girlsratio - scalefactor*boysratio}g more copper than zinc.

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The number of girls in the ratio.

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The total number of pupils in the dance school.

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The factor by which the ratio sum is multiplied to get the class size.

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The number of boys in the ratio.

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The increment which is added to boysratio to ensure that there are more girls.

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How much more copper than zinc is required to make {classsize}g of brass?

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