Interpret Pie Charts

Do you like to exercise?

 

 

A local gym offers four types of memberships: swim only, squash only, gym only or a full membership.

 

A gym employee analysed how many members got each type of membership and presented his findings in a pie chart:

 

 

Can we tell how many members have each type of membership?

 

Not from the information we have!

We can only tell which one is the most popular, the second most popular etc.

 

Let's say we know that there are 720 members altogether.

How could we find how many have the full membership?

 

 

Well, we can see that the gym only slice has an angle of 90°

A full turn (both in a circle or otherwise) is 360°

The whole pie represents the total number of members, i.e. 720

 

That means:

360° = 720 members

 

We can see that the full membership slice has an angle of 156°:

156° = ? members

 

So we have two equations that are proportionally related:

360° = 720 members

156° = ? members

 

How can we jump from 360 to 156?

 

We get a mid-step calculation of how many members are represented by 1° (though we could also use other angles if they work!).

To go from 360° to 1°, we divide by 360:

360° = 720 members

360° ÷ 360 = 720 ÷ 360

1° = 2 members

So each 1° represents 2 members.

 

How could we get how many members 156° degrees represent then?

We multiply 2 by 156!

 

1° = 2 members

156° = 312 members

 

So 312 members have the full membership.

 

Now grab your calculator and let's have a go at some questions!