Okay! Here we have an example of
a pie chart. We're gonna talk just a
little bit about some
interpretation issues that we have when
we're looking at pie charts.
In this particular pie chart here, I've
got an example
of a class that was being surveyed
to find out where they wanted to go on a
field trip.
In this case we have all of the
results of the class are displayed here and
They're just broken up into
different parts and portions.
Anytime that you have a whole and you know
about all of the parts we can use
a pie chart because a pie chart requires all 100
percent
of the data to be represented in the
actual visual that we see.
This works great in
this particular case.
Alright, in this question, or in this
problem, let's go ahead and see
some of the things that they might ask
you to do. In this case the question is
asking us how many students want to go
to the History Museum for their field
trip.
Let's look at what the pie chart
tells us. Look around for the history
museum, it's right here,
and we see this value right here and we
know that 30 percent
of the students would like to go to the
History Museum so we can put that in
here.
However this is really
actually not what the question is actually
asking us to find. Let's take a look up
here.
If it wanted to know what
percentage, the question is going to ask
what percentage.
In this case we have a slight variation
here. The question asks us how many
students want to go to the History
Museum for their field trip.
We do not have enough information to
answer this question right now.
All we know is that 30 percent of them
want to go. We have no idea,
without actually knowing how many
students there are in the class, we have
no idea about how to get this
information.
We need the total number of students
to be given for us to be able to figure
out a number
from a pie chart.
If, instead, we were told that there were
30 students in this class,
now we would have enough information to
actually be able to figure this out
We know that 30 percent of them want
to go to History Museum so 30 percent
of
the thirty students want to go to the
museum.
Now it's just a matter of remembering a few of our percentage things.
Anytime that we
have a percentage given in a problem, we
always need to convert it to a decimal
form before we do any calculations. For
30 percent, to change a percent to
decimal, we move the decimal
location, which right now is at the end
of the problem, we move it 2 places to
the left.
We can write 30 percent as .30
or just .3. The keyword "of" is a good
clue for
multiplication. So,
to figure this out we wanna find
30 percent or .3
of, so times, and then we just fill our 30 in. Do .3 times 30 on your
calculator
and we end up with a total of 9
students in the class
that would actually be interested in
going to the History Museum.
So again, pay attention to what your
question is asking.
If it asks you for a percentage, we can
find that information straight from our
pie chart.
If it asks us something about how many,
then we're actually going to need to know a number.
Because our pie chart only gives us percentages we would need to
know the total to be able to take that
next step
and actually come up with a solution are
looking for.
