Holt Geometry

1-1 Understanding Points, Lines, and Planes

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Holt Geometry

1-1 Understanding Points, Lines, and Planes

You will learn to:

Measure segments and determine accuracy of measurement.

Compute with measures.

1-2 Objectives

Line segment

Precision

Congruent

Vocabulary

Segments

Segments are measured from one endpoint to the other endpoint. The length of a segment is only as precise as the smallest unit on the measuring device.

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.

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 .

Each inch is divided into fourths. Point G is closer to the

-inch mark.

Answer: is about inches long.

Find the length of .

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

Answer: is about 3 inches long.

Answer: 18 mm

a. Find the length of

b. Find the length ofAnswer: 2 cm

c. Find the length of .Answer: in.

Find the precision for inches. Explain its meaning.

Answer: The precision is inch. The measurement could

be inches to inches.

The measuring tool is divided into -inch increments. Thus,

the measurement is precise to within inch.

PrecisionThe precision of any measurement depends on the smallest unit of measure available on the measuring tool. The measurement should be precise to within ½ of the unit of measure.

(⅛ higher or lower than 32¾)

Answer: The precision is 0.5 millimeter. The measurement could be 87.5 millimeters to 88.5 millimeters.

Answer: The precision is inch. The measurement

could be inches to inches.

PRECISION Find the precision for each measurement. Explain its meaning.

a. 88 millimeters

b.

Find LM.

Point M is between L and N.Sum of parts wholeSubstitutionSubtract 2.6 from each side.

Simplify.

Answer: is 1.4 centimeters long.

LM is the measure of .

a. Find SE.

Answer: in.

When segments have the same measure, they are said to becongruent.

Substitute known values.

Add 3 to each side.

Divide each side by 12.

Simplify.

Simplify.

Find x and ST if T is between S and U, ST 7x, SU 45, and TU 5x – 3.

Answer:

a. Find SE.

Answer: in.

b. Find ON.

Answer: 3.7 cm

c. Find a and AB if AB 4a + 10, BC 3a – 5, and AC 19.

Answer:

What did you learn today?

How to:

Measure segments and determine accuracy of measurement.

Compute with measures.

Assignment:

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