SOLUTION: For every 100 customers that came in the store 75 bought milk. If only 20 came in the store yesterday how many bought milk

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Question 620932: For every 100 customers that came in the store 75 bought milk. If only 20 came in the store yesterday how many bought milk
Answer by math-vortex(648) About Me  (Show Source):
You can put this solution on YOUR website!
Hi, there--
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This is a proportion problem. We want to know how many customers bought milk if only 20 customers came into the store.
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Let x be the number of customers who bought milk if only 20 customers came into the store.
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In the first case, the ratio of milk-buying customers to total customers is 75 to 100, or 75/100.
In the second case, the ratio is x to 20, or x/20.
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We set these ratios equal to each other to make a proportion. Then we solve for the value of x that makes the proportion true.
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75%2F100=x%2F20
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We can use the idea of scale factor to solve for x. First look at the two denominators. The scale factor from 100 to 20 is 1/5 because 100*(1/5)=20.
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The scale factor from 75 to x in the numerator must be the same since the ratios are equivalent. We multiply 75*(1/5) to find x. So x=15.
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In the context of this problem, x=15 means that 15 customers bought milk if only 20 customers came into the store.
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Hope this helps. Feel free to email me if you have questions about this solution.
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Ms.Figgy
math.in.the.vortex@gmail.com