Math 7 · Unit 2, Lesson 7
Circle Graphs
Reading percents from a pie.
I say it the way your test says it.
And I say it the way you would say it to a friend. Same idea, two ways.
Write it down. Do every step on paper, one line per step. Percent problems go wrong in your head, not on the page. If you changed something, it should be on the paper.
Go in order. Each tile has a short explanation, then a "Let me try a few" button.
When you have finished
At the end of each tile you will find a review form to give us feedback.
NC standards: NC.7.RP.3.
Words we use
| Word | Plain English | What you do |
|---|---|---|
| Circle graph | A circle cut into slices that show parts of a whole. | The whole circle is 100 percent. |
| Sector, or slice | One piece of the circle. | Read it as a percent and as degrees. |
| Degree | One 360th of a full turn. | Percent of 360 gives the degrees. |
| Whole | The entire circle: 100 percent and 360 degrees. | Every slice is a part of it. |
The big idea
A proportional relationship always multiplies by the same number, the unit rate.
Percent means out of 100. A percent is a unit rate for 100 instead of for 1: 30 percent means 30 for every 100.
This lesson added the picture. A circle graph splits a whole into slices, and the whole circle is both 100 percent and 360 degrees, so every slice has two names: a percent of the whole and an angle. Percent of 360 gives the degrees; degrees out of 360 gives the percent. To build a graph, each count over the total gives a percent. To read one backward, degrees to percent, then percent of the whole group. Every slice is a proportional relationship with the whole.
Exit ticket
On paper or an index card. Use the math word and the plain-English word.
- In a circle graph of 50 students, the slice for walking to school is 72 degrees. How many students walk?
- How many degrees is 40 percent of a circle?
- 12 of 30 students pick soccer. What percent, and how many degrees?
Check your exit ticket
- 10 students: 72 out of 360 is 20 percent, and 20 percent of 50 is 10.
- 144 degrees.
- 40 percent, 144 degrees.
Printables
The study guide for this lesson is also the study guide for all of Unit 2: Elle and Finn, both big-idea sentences, the percent, fraction, and decimal benchmarks, the three missing-piece types on the percent bar, the multipliers for adding on and taking off, percent change, and percents to degrees. Plus a worksheet with an answer key and a lesson plan that walks a parent or tutor through the three tiles.
Where this goes next
A percent decrease is a change that goes down. Unit 3 gives that kind of change a sign.
NC Grade 7 standards in this lesson: NC.7.RP.3.