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The pie chart shows the mathematics exam classifications of sixty students.
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Using the information on the pie chart, determine the number of students that received a pass grade.
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Now pie charts tell us all about proportion.
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They tell us the share of the whole population that fall into each category.
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Now with this particular group of students, it seems that a relatively small share, fifteen percent of them, scored just a pass grade.
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So fifteen percent of the sixty students scored a pass grade.
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It looks like the other eighty-five percent did even better than that, and scored either good, very good, or excellent.
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Anyway, to answer this question, we’ve got to calculate fifteen percent of sixty.
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Well this is something we can do in our heads.
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Ten percent of sixty is six.
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And fifteen percent of something is ten percent of something plus five percent of the same thing.
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And five percent is half of ten percent.
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So it’s easy to work out what five percent of sixty is.
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Five percent of sixty is half of ten percent of sixty, and half of six is three.
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So to work out fifteen percent, I just need to add the ten percent and the five percent.
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And six plus three is equal to nine.
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So our answer is: Nine students received a pass grade.