Linear Measure and Precision

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Lesson 1-2

• Linear Measure and Precision

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Transparency 1-2
5-Minute Check on Lesson 1-1

• Refer to the figure for questions 1 through 5.
• Name three collinear points.
• What is another name for AB?
• Name a line in plane Z.
• Name the intersection of Planes Z and W.
• How many lines are in plane Z?
• Three lines
  are coplanar. What is thegreatest number of
  intersection point that can occur?

Standardized Test Practice
A
C
B
D
2
3
4
5
Click the mouse button or press the Space Bar to
display the answers.
3
Transparency 1-2
5-Minute Check on Lesson 1-1

• Refer to the figure for questions 1 through 5.
• Name three collinear points.
• What is another name for AB?
• Name a line in plane Z.
• Name the intersection of Planes Z and W.
• How many lines are in plane Z?
• Three lines
  are coplanar. What is thegreatest number of
  intersection point that can occur?

A, T, B
AT or TB
AT or l
AB
2
Standardized Test Practice
A
C
B
D
2
3
4
5
Click the mouse button or press the Space Bar to
display the answers.
4
Objectives

• Measure segments and determine accuracy of
  measurement
• Compute with measures
• Sum of the parts equals the whole

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Vocabulary

• Line Segment has two end points and can be
  measured
• Precision is equal to one-half the smallest
  unit on the measuring tool
• Congruent when segments have the same measure,
  they are congruent (?)
• Equal numbers (variable and equations) and
  measurements of things are equal if the have the
  same values

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Example 2-1a
The long marks are centimeters, and the shorter
marks are millimeters. There are 10 millimeters
for each centimeter.
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Example 2-1b
The ruler is marked in centimeters. Point R is
closer to the 5-centimeter mark than to 4
centimeters.
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Example 2-1c
Answer 18 mm
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Precision
Precision ½ the smallest unit of measure on the
measuring device
Smallest Unit of Measure 1/8 th inch Precision
(1/8)/2 1/16 th inch String Length is 2 ¼
1/16 or between 2 3/16 and 2 5/16 inches long
Smallest Unit of Measure 2F Precision
(2F)/2 1F Temperature is 60F 1F
or between 59F and 61F
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Example 2-3a
Find the precision for 32¾ inches. Explain its
meaning.
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Example 2-3c
Answer The precision is 0.5 millimeter. The
measurement could be 87.5 millimeters to 88.5
millimeters.
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Whole Sum of its Parts

• Any distance can be broken into pieces and the
  sum of those pieces is equal to the whole distance

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6
11
32
The whole length, AD, is equal to the sum of its
parts, AB BC CD AD AB BC CD 32 11
14 6
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Example 2-4a
Find LM.
Point M is between L and N.
Substitution
Subtract 2.6 from each side.
Simplify.
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Example 2-4d
Find x and ST if T is between S and U, ST 7x,
SU 45, and TU 5x 3.
Substitute known values.
Add 3 to each side.
Simplify.
Divide each side by 12.
Simplify.
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Example 2-4h
c. Find a and AB if AB 4a 10, BC 3a 5,
and AC 19.
Answer a 2, AB 18
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Summary Homework

• Summary
• The precision of any measurement depends on the
  smallest unit available on the measuring device
• The measure of a line segment is the sum of the
  measure of its parts WHOLE SUM OF
  PARTS
• Homework
• pg 16-17 5, 8, 25, 29-31