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Measuring

Pick 6 strips of paper from the container.  Get a ‘ruler’.

With your partner, please measure and record the measurements of the items you chose from the bucket.

Your measurements need to be as accurate as possible – NOT ESTIMATES.

Measuring Length

How do you measure distance on a number line?

-3 -2 -1 0 1 2 3 4 5 6 7

What is the distance between -2 and 3 5

What is the distance between -2 and -7

What is the distance between 5 and 17

What is the distance between 0 and -5

What is the distance between 10 and -3

5

12

5

13

Notice that all the DISTANCES ARE POSITIVE!

What mathematical operation makes all answers positive?

ABSOLUTE VALUE!!!

♥ On a number line, the distance between the coordinates a and b is |a-b| or |b-a|.

♥ This will give you the measure of the segment.

Measuring length

a b

WRITE THIS DOWN

Notation for MEASURE of a segment

mXY or XY If you use the bar, use the m. If you don’t use the bar, don’t use the m

In this notation, we are talking about the LENGTH of the segment NOT the segment itself.

-3 -2 -1 0 1 2 3 4 5 6 7

X Y Z

mXY = |-3 - 0|

= |-3|

= 3

XZ = |-3 - 4|

= |-7|

= 7

CONGRUENT

• Means the same size and same shape

• The congruent symbol is =~

• Means the same size and same shape

• The congruent symbol is =~

A B C D AB CD ~=

A B

C D

E

Segment Congruence Postulate

♥ If two segments are congruent, then they have the same measure.

♥ The converse is also true :If two segments have the same measure,

then they are congruent.Are you able to write a biconditional?Remember…. A biconditional IS A

DEFINITION

A B

C D

E

~=

• The converse is also true:If AC = BD then AC BD

Important notation• If AC BD then AC = BD~=

•This says: if the segments are CONGRUENT then the measures are EQUAL.

Without the bar means NUMBER

AC is a NUMBER

AC is NOT

Segment Addition Postulate

If point R is between points P and Q, then PR + RQ = PQ

P R Q

A B C

3 5

AB + BC = AC

3 + 5 = AC

8 = AC

X + 3x + 1 = 25

4x + 1 = 25

4x = 24

X = 6

Find the measure of each segment and CHECK YOUR ANSWER

A B C

x 3x + 1 AC = 25

Let’s learn how to BISECTa segment

You need 1 piece of patty paper straight edge compass

Your assignment

2.2/2.3packet