Warm-up
Three quick questions from earlier lessons.
Discover
In a circle graph, a sector takes up half of the circle. What percent of the data is it?
- 50%
- 180%
Key idea
A circle graph shows parts of one whole.
Each sector is a percent of the whole, and the whole circle is 100% (or 360°). To find a count, take that percent of the total. To find a sector's angle, take that percent of 360°.
Worked example
40 students; the music sector is 25%.
25% of 40 = 10 students
Count.
25% of 360° = 90°
Angle.
Your turn, guided
Your turn: 60 people, a sector of 10%. How many people?
10% of 60.
Practice ★
- A circle graph shows the favorite sports of 240 students. The soccer sector is labeled 15%. How many students chose soccer?
- A circle graph shows the favorite sports of 60 students. The soccer sector is labeled 40%. How many students chose soccer?
- A circle graph shows how 160 students get to school: bus 50%, walk 25%, car 25%. Which statement is true?
- Twice as many students take the bus as walk
- 50 students take the bus
- The sectors add up to 360 students
Watch out!
Practice ★★
- A category is 10% of a circle graph. What is the angle of its sector, in degrees?
- A category is 45% of a circle graph. What is the angle of its sector, in degrees?
- A circle graph shows the favorite sports of 240 students. The soccer sector is labeled 15%. How many students chose soccer?
Exit ticket
Three questions to check you have got it.
- A circle graph shows the favorite sports of 240 students. The soccer sector is labeled 15%. How many students chose soccer?
- A circle graph shows the favorite sports of 60 students. The soccer sector is labeled 40%. How many students chose soccer?
- A circle graph shows the favorite sports of 40 students. The soccer sector is labeled 35%. How many students chose soccer?
Summary card
Circle graphs
Count = percent × total; angle = percent × 360°.
Watch out: a percent is not a count.
End of the lesson
Next lesson: Measures of center: mean and median Back to the chapter