1-2 Linear Measure

You identified and modeled points, lines, and planes.

• Measure segments.

• Calculate with measures.

Definition

Line segment – a measurable part of a line that consists of 2 points (end points) and all of the points between them.A line segment is named by its 2 end points . It can be read right to left or left to right.

is read line segment AB or line segment BA.

The measure (length)of a line segment is written without the bar over the top of the 2 letters.

A B

Length in Metric Units

A. Find the length of AB using the ruler.

The ruler is marked in millimeters.

Point B is closer to the 42 mm mark.

Answer: AB is about 42 millimeters long.

Length in Metric Units

B. Find the length of AB using the ruler.

Each centimeter is divided into fourths.

Point B is closer to the 4.5 cm mark.

Answer: AB is about 4.5 centimeters long.

A. 2 mm

B. 1.8 mm

C. 18 mm

D. 20 mm

Length in Standard Units

Each inch is divided into sixteenths. Point E is closer to the 3-inch mark.

A.

Measure in centimeters unless directions specify unit of measure.

B.

A.

A.

B.

C.

D.

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Betweeness of points – for any 2 points , there is a real point between the 2 points.

A B C

Find Measurements by Adding

Find XZ. Assume that the figure is not drawn to scale.

XZ is the measure of XZ. Point Y is between X and Z. XZ can be found by adding XY and YZ.

___

Add.

A. 16.8 mm

B. 57.4 mm

C. 67.2 mm

D. 84 mm

Find BD. Assume that the figure is not drawn to scale.

B

C

D

16.8 mm

50.4 mm

Find Measurements by Subtracting

Find LM. Assume that the figure is not drawn to scale.

Point M is between L and N.

LM + MN = LNBetweenness of points

LM + 2.6 = 4Substitution

LM + 2.6 – 2.6 = 4 – 2.6 Subtract 2.6 from each side.

LM = 1.4 Simplify.

Find TU. Assume that the figure is not drawn to scale.

TU

V3 in

A.

B.

C.

D.

in.

in.

in.

in.

Write and Solve Equations to Find Measurements

ALGEBRA Find the value of x and ST if T is between S and U, ST = 7x, SU = 45, and TU = 5x – 3.

ST + TU = SU Betweenness of points

7x + 5x – 3 = 45 Substitute known values.

7x + 5x – 3 + 3 = 45 + 3 Add 3 to each side.

12x = 48 Simplify.

Draw a figure to represent this situation.

x = 4 Simplify.

ST = 7x Given

= 7(4) x = 4

= 28 Multiply.

Answer: x = 4, ST = 28

Now find ST.

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Congruent segments – segments that have the same measure.

The Geometry symbol for congruent is “≈”

Definition

A. barbecuing and beach

B. board games and museums

C. beach and picnic

D. zoo and board games

LEISURE ACTIVITIES The graph shows the percent of adults who participated in selected activities. Suppose a segment was drawn along the height of each bar. Which categories would have segments that are congruent?

Constructions

Constructions are a method of creating Geometric figures by using a pencil, compass, and straightedge.

Drawings are created using measuring tools-rulers, protractors.

Sketches are created without the use of any tools.

Copy a segment

1. Draw a segment to be copied.2. Draw a line on your paper with a dot near one end.3. Place the sharp point of the compass at one end point

of the segment.4. Open up the compass so the pencil matches the other

end of the segment.5. Without moving the compass, move it to the dot and

make an arc through the line.A congruent segment has been constructed.

P. 18: 10-16 even, 22, 24, 28, 30, 46-50

Assignment 1-2