Lesson 1-2
Linear Measure and Precision
5-Minute Check on Lesson 1-1
Transparency 1-2
Refer to the figure for questions 1 through 5.
1. Name three collinear points.
2. What is another name for AB?
3. Name a line in plane Z.
4. Name the intersection of Planes Z and W.
5. How many lines are in plane Z?
6.
Three lines are coplanar. What is the
greatest number of intersection point that can occur?
Standardized Test Practice:
A
2
B
3
C
4
D
5
Click the mouse button or press the
Space Bar to display the answers.
Transparency 1-2
5-Minute Check on Lesson 1-1
Refer to the figure for questions 1 through 5.
1. Name three collinear points.
A, T, B
2. What is another name for AB?
3. Name a line in plane Z.
AT or TB
AT or l
4. Name the intersection of Planes Z and W.
5. How many lines are in plane Z?
6.
AB
2
Three lines are coplanar. What is the
greatest number of intersection point that can occur?
Standardized Test Practice:
A
2
B
3
C
4
D
5
Click the mouse button or press the
Space Bar to display the answers.
Objectives
• Measure segments and determine accuracy of
measurement
• Compute with measures
– Sum of the parts equals the whole
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
Find the length of
.
The long marks are centimeters, and the shorter marks are
millimeters. There are 10 millimeters for each centimeter.
Answer:
is about 42 millimeters long.
Find the length of
.
The ruler is marked in centimeters. Point R is closer to the
5-centimeter mark than to 4 centimeters.
Answer:
is about 5 centimeters long.
a. Find the length of
Answer: 18 mm
2 ¼ ½ ¾
3 ¼ ½ ¾
4
Precision
Precision – ½ the smallest unit of
measure on the measuring device
70°F
Smallest Unit of Measure = 1/8 th inch
Precision = (1/8)/2 = 1/16 th inch
60°F
String Length is 2 ¼ ± 1/16 or
between 2 3/16 and 2 5/16 inches long
50°F
1 ¼ ½ ¾
40°F
Smallest Unit of Measure = 2°F
Precision = (2°F)/2 = 1°F
Temperature is 60°F ± 1°F or
between 59°F and 61°F
Find the precision for 32¾ inches. Explain its meaning.
The measuring tool is divided into
-inch increments. Thus,
the measurement is precise to within
Answer: The precision is
be
inches to
inch.
inch. The measurement could
inches.
PRECISION Find the precision for each measurement.
Explain its meaning.
a. 88 millimeters
Answer: The precision is 0.5 millimeter. The measurement
could be 87.5 millimeters to 88.5 millimeters.
b.
Answer: The precision is
could be
inch. The measurement
inches to
inches.
Whole = Sum of its Parts
Any distance can be broken into pieces and
the sum of those pieces is equal to the whole
distance
14
11
A
B
6
C
D
32
The whole length, AD, is equal to the sum of its
parts, AB + BC + CD
AD = AB + BC + CD
32 = 11 + 14 + 6
Find LM.
LM is the measure of
.
Point M is between L and N.
Sum of parts
whole
Substitution
Subtract 2.6 from each side.
Simplify.
Answer:
is 1.4 centimeters long.
Find x and ST if T is between S and U, ST = 7x, SU = 45,
and TU = 5x – 3.
5x – 3
U
7x
T
S
Substitute known values.
Add 3 to each side.
Simplify.
Divide each side by 12.
Simplify.
c. Find a and AB if AB = 4a + 10, BC = 3a – 5, and AC = 19.
3a – 5
4a + 10
A
Answer: a = 2, AB = 18
B
C
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