How Do You Make a Circle Graph or Pie Chart?Date: 12/16/2003 at 21:33:46 From: twa Subject: circle graph How do I make a circle graph using these numbers? I'm thinking of a circle and it has each percent inside and a key. body part weight (pounds) head 10.5 neck and trunk 70.0 arms 16.5 hands 2.5 legs 47.5 feet 5.0 Date: 12/17/2003 at 11:39:42 From: Doctor Jason Subject: Re: circle graph Hi Twa, Of all of the different types of graphs, circle graphs are one of the more complicated ones to make. They are sometimes called pie charts. Instead of using your information, let's look at an example using the following set of data regarding eye color of students in a class: Eye color | # of Students --------------------------- Brown | 15 Blue | 9 Green | 6 To make a circle graph using this set of data, the first thing I would do is make each of the numbers into a fraction out of the total number of students. There is a total of 30 students in the class (15 + 9 + 6): Eye color | # of Students | Fraction ------------------------------------- Brown | 15 | 15/30 Blue | 9 | 9/30 Green | 6 | 6/30 ------------------------------------- Total | 30 | 30/30 The circle graph will have 3 "pie pieces," one for each eye color. The part representing brown eyes will be 15/30 of the circle, the part representing blue eyes will be 9/30 of the circle, and the part representing green eyes will be 6/30 of the circle. How do we know how much 15/30 of the circle is? The answer lies in the fact that a circle is 360 degrees. If we multiply the fraction representing the part of the circle times 360, we will then have the angle measure of the respective part. It may be easier to work with decimals instead of fractions, so I divided out the fractions and entered them in our table: Eye color | # of Students | Fraction | Decimal ------------------------------------------------ Brown | 15 | 15/30 | 0.5 Blue | 9 | 9/30 | 0.3 Green | 6 | 6/30 | 0.2 ------------------------------------------------ Total | 30 | 30/30 | 1.0 Multiplying the decimal number times 360 gives us the angle measure of each part of the graph: 360 * 0.5 = 180 (Brown) 360 * 0.3 = 108 (Blue) 360 * 0.2 = 72 (Green) Entering these values into the table: Eye color | # of Students | Fraction | Decimal | Angle Measure ---------------------------------------------------------------- Brown | 15 | 15/30 | 0.5 | 180 degrees Blue | 9 | 9/30 | 0.3 | 108 degrees Green | 6 | 6/30 | 0.2 | 72 degrees ---------------------------------------------------------------- Totals | 30 | 30/30 | 1.0 | 360 degrees Now we can construct our graph. We need to draw a circle with one radius. Using the radius as one leg of the angle, draw the second segment of the angle using a protractor and one of the angle measures from the table. If we use 180 degrees as the first angle, our circle should be cut in half, since 180 is a straight line. Next, we use one of the remaining angle measures to draw another angle. One of the legs of this angle needs to be one of the 2 radii already drawn (but not drawn as part of the 180 degree "brown" piece, meaning don't overlap the angles). After that, the remaining piece should have the angle measure of the remaining angle in the table (It would be a good idea to check!). Finally, give the graph a name and provide a key or labels. You may also want to color the graph. I hope this helps! Let me know if there is anything else I can do. - Doctor Jason, The Math Forum http://mathforum.org/dr.math/ |
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