Circle Graphs 04:25 minutes

Video Transcript

Transcript Circle Graphs

Every year, the Griswald family goes on vacation to get away from their city with its blinding lights. Usually, the Griswalds go to a campground in California known for their Joshua trees - and it’s where Mom and Dad Griswald first met and fell in love. Mom thinks it’s romantic, but the kids? Not so much. Since it's such a beautiful day, the Griswald family decides to go try a different place in southern California, but they just can’t agree on where to go, what to do OR how to get there.To decide, Grandma Griswald suggests they spin a vacation wheel, and Dad Griswald says to make it fair, the family should use a circle graph, also known as a pie graph.

Setting up a table

How should the Griswalds do this? Grandma Griswald makes a table and lists the vacation destination choice for each of the 8 family members. Each person can only vote for one destination. 2 out of 8 want to go to the camp ground with the Joshua trees - again, 3 out of 8 Griswalds want to go to the P.I. Museum. 2 want to go to the beach to see every breaking wave and 1 desires to go to Anaheim. There is also a column listing the percentages: 37.5% want to go to the P.I. Museum, 25% want to go camping, 25% want to go to the beach and 12.5% want to go to Anaheim.

Drawing a graph

To draw the graph, we need to divide the circle into sectors to represent the various choices. Remember, a sector looks like a slice of pie. Let’s calculate the central angle of each sector. We'll use the fraction of the number of people and their corresponding choice to figure out the central angle for each sector: 2 out of 8 want to go camping, so multiply two-eighths times the angle measure of a full circle, 360°. The sector will have a central angle of 90°. Okay, now we'll do this for each sector, and then we can use the angle measurements to set up the graph. An advantage of circle graphs is that they also identify the percentage of each sector. This graph is looking good and Dad is ready to spin. The Griswalds are going to Anaheim!

Next choice, when to go. Take a look at the table. The grandparents are retired, so they don’t care when the vacation happens, they just want to spend time with the family. So only 6 family members will vote this time. Let’s see, 3 want to go during Summer 2 want to go in Spring and 1 wants to go during final exam week.

Now, let's figure out the central angles. You could also use the percent to calculate the central angle for each sector, but because of rounding errors, the fraction method may be the most accurate. Okay! Let’s calculate! Set up the graph, label each sector, adjust the central angle. and spin. This is going to be an interesting vacation. The Griswalds are going sightseeing in southern California this summer!

One last choice. How to actually get to southern California: 3 want to fly, 2 want to drive, 2 want to ride skateboards, and 1 wants to be teleported. Dad throws out the teleportation choice for obvious reasons. So we’ll calculate the angles as parts of seven. Dad is ready for the final spin and the Griswald family will take skateboards to southern California. Skateboards, hmm. I hope Grandma and Grandpa Griswald don't get vertigo. Off they go on their summer vacation on skateboards. Whoa! Look at Granny Griswald grind! I guess that answers our question about who else voted for skateboards!