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Section 1-4

Calculating, Estimating, andReading Graphs

CALCULATING, ESTIMATING, AND READING GRAPHS

• Calculation• Estimation• Interpretation of Graphs

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CALCULATION

There are many types of calculators such as four-function, scientific, and graphing.

There are also many different models available and you may need to refer to your owner’s manual for assistance. Other resources for help are instructors and students that have experience with that model.

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EXAMPLE: CALCULATION

Use your calculator to find the following:a) b)c)

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2601

41.5

Solutiona) 3.14159265 (approximately)b) 51c) 5.0625

ESTIMATION

There are many times when we only need an estimate to a problem and a calculator is not necessary.

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EXAMPLE: ESTIMATION

A 20-ounce box of cereal sells for $3.12. Approximate the cost per ounce.

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SolutionBecause it is an approximation, we can say that the cost is about $3.00 for 20 ounces. This works out to 3.00/20 = $0.15 per ounce.

INTERPRETATION OF GRAPHS

Using graphs is an efficient way to transmit information. Some of the common types of graphs are circle graphs (pie charts), bar graphs, and line graphs.

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EXAMPLE: CIRCLE GRAPH (PIE CHART)

Use the circle graph below to determine how many of the 140 students made an A or a B.

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A 15%

D 10%

C 40%

B 25%

F 10%

Letter Grades in College Algebra

CIRCLE GRAPH (CONTINUED)

SolutionNotice that there were 15% A’s and 25% B’s.For 140 students this yields:

A: 0.15 x 140 = 21B: 0.25 x 140 = 35

which is a total of 56 students.

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EXAMPLE: BAR GRAPH

The bar graph shows the number of cups of coffee, in hundreds of cups, that a professor had in a given year.

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0

2

4

6

8

10

2001 2002 2003 2004 2005

Cup

s

(in

hun

dred

s)

a) Estimate the number of cups in 2004b) What year shows the greatest decrease in cups?

BAR GRAPH (CONTINUED)

Solutiona) The number of cups in 2004 appears to be

about 700.b) The year 2005 looks to have the greatest

decrease at about 250 cups.

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EXAMPLE: LINE GRAPHThe line graph shows the average class size of a first grade class at a grade school for years 2001 through 2005.

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14

18

22

26

30

34

Stu

dent

s pe

r cl

ass

’01 ’02 ’03 ’04 ’05

a) In which years did the average class size increase from the previous year?b) How much did the average size increase from 2001 to 2003?

LINE GRAPH (CONTINUED)

Solutiona) The average class size increased in years 2002,

2003, and 2004.b) The average class size was 16 in 2001 and 28 in

2003 which would indicate an increase of 12 students per class.

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