2. THE PRECISION OF A MEASUREMENT IS DEPENDENT
ON THE TOOL BEING USED TO MAKE THE MEASUREMENT.
THE MEASUREMENT SHOULD BE PRECISE TO ½ OF THE
SMALLEST UNIT ON THE TOOL.
IF OUR SMALLEST UNIT IS AN INCH,
WE’LL SAY WE’RE PRECISE TO ½ INCH.
IF OUR SMALLEST UNIT IS A HALF INCH,
WE’LL SAY WE’RE PRECISE TO 1/4 INCH.
3. A LINE SEGMENT IS PART OF A LINE.
A SEGMENT HAS 2 ENDPOINTS.
WE NAME A SEGMENT BY THESE 2 POINTS
AND THE ORDER DOESN’T MATTER.
A
B
D
∙
∙
∙C
∙
THE POINTS FROM A TO B
ARE SEGMENT AB OR BA.
THE POINTS FROM C TO D
ARE SEGMENT CD OR DC.
OTHER SEGMENTS
AC , BD , BC , AD
4. m AX + m XB = m AB OR
AX + XB = AB
AB - AX = XB
BIG – LITTLE = LITTLE
A
X
B
●
●
●
THE SEGMENT ADDITION POSTULATE LETS US GIVE A NAME TO AN
OPERATION THAT WE’LL USE OFTEN DURING GEOMETRY.
LITTLE + LITTLE = BIG
AX = Y+3
XB = 3Y
AB = 23
LITTLE + LITTLE = BIG
Y+3 + 3Y = 23
4Y + 3 = 23
4Y = 20
Y = 5
5. CONGRUENT SEGMENTS
IF 2 FIGURES ARE CONGRUENT, ALL THEIR MEASUREMENTS
ARE EQUAL. IF 2 SEGMENTS ARE CONGRUENT,
THEIR LENGTHS ARE EQUAL.
A B C
• • •
AB = BC
~
6. IF A MEASUREMENT IS REPRESENTED OR NAMED 2 DIFFERENT WAYS,
THEN THE 2 AMOUNTS ARE EQUAL.
H F G
• • •
FIND FG IF HF = 3X, FG = 12X and HF = 15
WE CAN’T USE LITTLE + LITTLE = BIG, WHY?
HF IS NAMED 2 WAYS SO….
3X = 15
X = 5
FG = 12(5) = 60
7. 1. Find MN if N is between M and P, MN = 5X - 4, NP = 4X + 6 and MP = 47
2. Find WY if X is between W and Y, WX = 3A + 2, XY = 30, and WY = 10A + 11
3. Find the precision for a measurement of 32 meters.
4. What is an acceptable range for a measurement of 51.5 inches?
5. Find AC if C is between A and B and AC = 2X + 4, CB = AC and AB = 3X + 17
LITTLE + LITTLE = BIG
5X – 4 + 4X + 6 = 47
9X + 2 = 47
X = 5
MN = 5(5) – 4 = 21
LITTLE + LITTLE = BIG
3A + 2 + 30 = 10A + 11
3A + 32 = 10A + 11
3 = A
WY = 10(3) + 11 = 41
.5 METERS
51.25 TO 51.75 INCHES
2 ( 2X + 4 ) = 3X + 17
4X + 8 = 3X + 17
X = 9
AC = 2(9) = 18
