Mathematics
Grade 9
15 min
Interpret circle graphs
Interpret circle graphs
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Calculate the absolute value of a sector given its percentage and the total value.
Determine the central angle of a sector using its percentage.
Calculate the percentage of a sector given its absolute value and the total value.
Compare and contrast different sectors within a single circle graph to draw conclusions.
Solve multi-step problems by synthesizing information from a circle graph and accompanying text.
Evaluate the validity of statements made about data presented in a circle graph.
Ever wonder where your monthly allowance or part-time job earnings actually go? 💸 A circle graph can show you in a single glance!
This tutorial will teach you how to read and interpret circle graphs, also known as pie charts. You will learn how to translate the percen...
2
Key Concepts & Vocabulary
TermDefinitionExample
Circle Graph (Pie Chart)A circular statistical graphic divided into sectors to illustrate numerical proportion. The entire circle represents 100% of the data.A chart showing that 50% of students prefer pizza, 25% prefer burgers, and 25% prefer tacos.
SectorA wedge-shaped section of a circle graph that represents a specific category or part of the whole.In a budget graph, the 'Rent' sector might take up 40% of the circle.
PercentageA number or ratio expressed as a fraction of 100. In a circle graph, all sector percentages must add up to 100%.If 15 out of 60 students play soccer, the percentage is (15/60) * 100 = 25%.
Central AngleThe angle formed at the center of the circle by the two radii that define a sector. The sum of all central angles in a circle grap...
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Core Formulas
Finding the Part Value
Part = \frac{Percentage}{100} \times Total
Use this formula to find the actual numerical value of a sector when you know its percentage and the total value for the entire graph.
Finding the Central Angle
Central\ Angle = \frac{Percentage}{100} \times 360°
Use this formula to calculate the angle of a sector at the center of the circle. This is useful for constructing or analyzing the geometry of a circle graph.
Finding the Percentage
Percentage = \frac{Part}{Total} \times 100\%
Use this formula when you know the actual value of a category (the Part) and the Total value, and you need to find what percentage it represents.
4 more steps in this tutorial
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Challenging
A survey shows how 2,000 people spend their leisure time. The 'Reading' sector is 15% and the 'Sports' sector is 35%. The 'Other' category is composed of 'Gaming' and 'Socializing' in a 2:3 ratio, respectively. How many people chose 'Socializing'?
A.400
B.500
C.600
D.1000
Challenging
In a circle graph of a store's inventory, the 'Electronics' sector is 40% and the 'Apparel' sector is 25%. If there are 120 more electronic items than apparel items, what is the total number of items in the store's inventory?
A.600
B.800
C.1200
D.1500
Challenging
A city's annual budget is $10 million. A circle graph shows the allocation: Public Works (40%), Safety (35%), Parks (15%), Admin (10%). If the 'Safety' budget is increased by $500,000 (taken from the city's reserve, so the total budget for this graph effectively increases), what will be the new central angle for the 'Safety' sector?
A.126.0°
B.132.5°
C.137.1°
D.144.0°
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