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Last week, Olivia bought one gallon of milk for three dollars 50.
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This week, she bought two gallons of milk for seven dollars 50.
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Is the total money she paid proportional to the number of gallons?
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So what we need to think about is this word here “proportional” cause we has to decide “is the total money she paid proportional to the number of gallons?”
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So if it is to be proportional and we have one gallon is equal to three dollars 50, then if we wanted two gallons, the price should be double.
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If we wanted four gallons, the price should be multiplied by four.
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So let’s see if that’s the case.
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Well, if we’ve got one gallon for three dollars 50 and we want two gallons, then what we need to do is multiply each side of the equation by two.
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So one multiplied by two gives us two gallons.
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Then, we have to multiply three dollars 50 by two.
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Well, if we multiply three dollars 50 by two, we’re gonna get seven dollars.
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We can do that with some mental arithmetic because if we multiply three by two, that will give us six.
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And if we multiply 50 cents by two, that will give us one dollar.
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So six dollars plus one dollar gives us seven dollars.
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However, this wasn’t the price that Olivia paid because Olivia bought two gallons of milk for seven dollars 50.
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So therefore, we can say and answer the question “the relationship is not proportional.”
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So the total money she paid is not proportional to the number of gallons, because if it was, two gallons should have cost seven dollars.
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However, two gallons cost seven dollars 50.