7th Grade Math

Lesson 3B Statistical Displays 515

a. SCIENCE The table shows the

Composition of Earth’s Atmosphere

Element Percent

Nitrogen 78%

Oxygen 21%

Other gases 1%

present composition of Earth’s

atmosphere. Display the data in

a circle graph.

When constructing a circle graph, you first may need to convert the

data to ratios and decimals and then to degrees and percents.

Construct a Circle Graph

ANIMALS The table shows endangered

species in the United States. Make a circle

graph of the data.

• Find the total number of species.
  68 + 77 + 14 + 11 = 170


• Find the ratio that compares each number
  with the total. Write the ratio as a decimal
  rounded to the nearest hundredth.
  mammals: 17068 = 0.40 birds: 17077 ≈ 0.45

reptiles: 17014 ≈ 0.08 amphibians: 17011 ≈ 0.06

• Find the number of degrees for each section of the graph.
  mammals: 0.40 " 360° = 144°



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Endangered Species

birds: 0.45 " 360° ≈ 162°

reptiles: 0.08 " 360° ≈ 29°

amphibians: 0.06 " 360° ≈ 22°

Because of rounding, the sum of the degrees is 357°.

• Draw the circle graph. Label each
  piece with the title and percent.
  Label the graph with a title.
  Check After drawing the first three
  sections, you can measure the
  last section of a circle graph to
  verify that the angle has the
  correct measure.

b. OLYMPICS The number of Winter

Olympic medals won by the U.S. from

U.S. Winter Olympic Medals

Type Number

Gold 78

Silver 81

Bronze 59

1924 to 2006 is shown in the table.

Display the data in a circle graph.

Species

Mammals

Birds

Reptiles

Amphibians

68

77

14

11

Number of

Species

Real-World Link

The Carolina Northern

and Virginia Northern

Flying Squirrel are both

endangered. The

northern flying squirrel

is a small nocturnal

gliding mammal that is

about 10 to 12 inches

in total length and

weighs about

3–5 ounces.

RR

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