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