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### Course: Class 10 > Unit 5

Lesson 4: Reading and drawing pie charts# Reading pie graphs (circle graphs)

Reading Pie Graphs (Circle Graphs). Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

- Are there other ways to graph besides pie graphs, bar graphs, line graphs and the like, I am interested in the subject? I know there one really cool way of graphing at http://resourcetepee.com/ and I think it's neat (the site is really cool about graphs)(16 votes)
- you can also practice with pictographs, histograms and stuff. i like pictographs cuz they're really fun!(10 votes)

- Can it be split into diffrent 25%(10 votes)
- Yes, because it may be split in different ways or in the same way.(2 votes)

- what is the total of a pie graphs(5 votes)
- No, really the sum depends on the problem but if you simplify the result is 100% alway... I'm 100% sure(2 votes)

- How would we interpret the pie chart if the question came like this? :

"We have asked 90 people about their favourite football location. Their answers were : Southern England = 144 degrees, Northern England = 96 degrees, London = 32 degrees and Midlands = 88 degrees. How many people like each of the country?"(5 votes)- 1. Find out that how many degrees does 1 person takes in the graph (360/90=4)

2. Find out how many people in each category/buckets/bins (for example, to find out how many people like Southern England as a football location, we take the degrees of people that likes Southern England as a football location, which is 144 degrees, divide by the number of degrees that 1 person takes in this graph, which is 4, then the quotient is 144/4=36. (Sorry if this is too long)(6 votes)

- What happens when you are doing a pie chart of really bigger numbers?(3 votes)
- It does not matter how big the numbers are, all that matters is the proportion of the numbers and the way you divide the circle to make your pie chart(4 votes)

- what do the colors stand for(3 votes)
- The colors basically to make the graphs easier to visualize and interpret the data, and it's important to color it correctly, if not then it won't be as easy to visualize the data. So it does have a pretty significant role in the pie charts

Ps: My name is a tank(2 votes)

- Can you make a video of how to make Pie Graphs(3 votes)
- Why are they even called pie graphs?(1 vote)
- Because the graph is round which looks like a pie, have different parts which looks like a pie slice so we call it pie charts.(2 votes)

- What about drawing pie charts(1 vote)
- Each slice of the pie chart takes up a certain percentage of the total area, for example 12%, and then we know that the angle is going to be 12% of a full rotation,

or 0.12 × 360° = 43.2°.

Then we just use a protractor to construct that angle.(2 votes)

## Video transcript

For the past year,
a travel agency has collected data about the
number of individual tickets that it sells for its signature
product, a Mediterranean cruise. The monthly data on ticket
sales is shown below. What are the best and worst
months for cruise sales? So what they have
given us, this diagram. This is usually called
a pie chart or pie graph because it looks
like a pie that's sliced up into a
bunch of pieces. Sometimes this is
called a circle graph. But pie graph is
much more common. And then they say it's
monthly ticket sales. So each of these
slices represent the sales in a given month. So for example, this
blue slice over here represents the sales in January. And the way that a
pie chart is set up, each slice is bigger
or smaller, depending on what fraction of the
whole it represents. So for example, they're
telling us in January they sold 18% of the total
year's ticket sales in January. So if you add up all
of these percentages, it should add up to 100%. And not only do they tell
us that they sold 18%, but the slice of
this pie should be 18% of the area
of the entire pie. It is literally 18% of the pie. If you were to eat
this slice, you would have eaten 18% of the pie. Now with that out of
the way, let's think about their questions. What are the best and the
worst months for cruise sales? So the best month is obviously
the month where they sell, where they have the largest
percentage of their tickets were sold. And actually, I started with
January, and if you just-- and this is what's
neat about pie graphs. You wouldn't even have
to look at the numbers, January just jumps out as
the biggest slice of pie. If you didn't even
see the numbers, if you couldn't even read,
and you just looked at this and someone said what is
the largest slice of pie? You would immediately
say this is clearly the largest slice of
pie right over there. And so that is actually the
best month for cruise sales because they sold 18%. You see this 18%
is larger than all of the other
percentages over here. But it's clear, just by
looking at the graph, this is the largest slice. Now what's the worst month
for cruise ticket sales? Well, then we just have to
find the thinnest slice of pie. And if we look over
here, the slices of pie get pretty thin out down here. This is in the summer, in
June and July, and in May. But the smallest are
actually July and June. And this is where the
numbers become useful. Because when you just
eyeball it, you're not sure, hey, are these exactly the same? Or do they just look
exactly the same? And that's where these
numbers are valuable. And based on the data
they've given us, it looks like these are
tied for the worst in terms of ticket sales. In both of these months they
sell only 3% in each month. So the worst months for cruise
sales are July and June. July and June are
tied for the worst. The best is clearly January,
and then after January the next best-- they're
not really asking us that, but since we have the
pie chart in front of us, might as well ask ourselves
that, what's the next best? Well it looks like November is
slightly better than December. But in general,
it's pretty clear that the winter months do much
better in terms of cruise sales than these over here. And I guess people are looking
to get away from the cold.