Question Video: Reading Data from a Pie Chart Involving Percentage Mathematics

The pie chart shows the favourite subjects of students in a class. Using the information given on the pie chart, determine the percentage of students who chose English.

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Video Transcript

The pie chart shows the favourite subjects of students in a class. Using the information given on the pie chart, determine the percentage of students who chose English.

We know that the angles in a circle or at a point sum to 360 degrees. In this case, our four angles 126 degrees, 95 degrees, 67 degrees, and 72 degrees add up to 360. In this question, we’re interested in the students who chose English. This is represented by the blue sector of the pie chart. As the English sector was equal to 72 degrees, we can say that 72 out of 360 degrees represents English.

We were asked to give our answer as a percentage. And one way of converting from a fraction to a percentage is by multiplying by 100. The word percent means out of 100. We could type this directly into our calculator, which would give us an answer of 20.

Alternatively, we could do it in two steps. We could firstly convert the fraction into a decimal. 72 over 360 is the same as 72 divided by 360. This is equal to 0.2. We could then multiply 0.2 by 100 by moving all the digits two places to the left. Once again, this gives us an answer of 20. 20 percent of the students in the class said that their favourite subject was English.

An alternative method would’ve been to simplify the fraction 72 out of 360. Remember, when simplifying a fraction, whatever we do to the numerator we must do to the denominator. Both the numerator and denominator are divisible by 36. Two times 36 is equal to 72. Therefore, 72 divided by 36 equals two. 360 divided by 36 is equal to 10. Therefore, the fraction 72 out of 360 simplifies to two out of 10, or two-tenths.

We know that the fraction one-tenth is equal to 10 percent. Therefore, two-tenths will be double this. Once again, we have proved that the fraction 72 out of 360 is equal to 20 percent. The fraction two-tenths could have been simplified further to one-fifth. However, this is not required in this case.

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