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In a language class, the girl to boy ratio is 5 to 8.
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So for every 5 girls, we have 8 boys.
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If there are a total of 65 students,
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how many girls are there?
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So this is interesting.
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They give us the ratio of girls to boys.
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But then they want us to think about how many
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girls there are given that there are 65 total students.
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So what we really want to think about
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is not just the ratio of girls to boys – we want
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to think about the ratio of girls to total students.
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So how can we figure out
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what this ratio's going to be?
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Well the girl-to-boy ratio gives us a good clue.
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If there are 5 girls for every 8 boys, how many total
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students are there going to be for every 5 girls?
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Well for every 5 girls, you're going to have
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5 girls and 8 boys.
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You're going to have 13 total students.
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So I just added the 5 and the 8 right over here.
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The ratio of girls to total students is 5 to 13.
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One way of thinking about it is if you were
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to evenly divide the students into groups of 13,
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every group of 13 students would have 5 girls.
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Now, I think we're ready to figure out
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how many total girls there are.
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Because they tell us that there are 65 students.
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So, we don't just have one group of 13,
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we have 65 students.
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And how many groups of 13 are in 65?
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Well to go from 13 to 65, you have to multiply by 5.
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5 × 10 is 50 and 5 × 3 is 15. Right.
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So, 13 × 5 is 65.
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So essentially, one way you could view it is
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you have 5 groups of 13.
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So if you have 5 groups of 13,
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each of those are going to have 5 girls.
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Multiply by 5, and you're going to have 25 girls.
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So for every 65 students,
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you're going to have 25 girls,
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given the information that has been given.