2-2: SEGMENTS AND PROPERTIES OF REAL NUMBERS

2-2: Segments & Properties of Real Numbers

BETWEENNESS: A point is between two points if and only if all three points are collinear, and the two points are on opposite sides of the third point.

Point K is between points A and L, because A, K & L are all on the same line and AK + KL = AL

Point B is not between points A and D, because B is not on the same line as A & D

A

B

K

M

S

L D

2-2: Segments & Properties of Real Numbers

Example Points A, B, and C are collinear. If AB = 12,

BC = 47, and AC = 35, determine which point is between the other two. Check to see which two measures add to equal

the third. 12 + 35 = 47 AB + AC = BC Therefore, point A is between points B and C

Points R, S and T are collinear. If RS = 42, ST = 17, and RT = 25, determine which point is between the other two. Point T

2-2: Segments & Properties of Real Numbers

Some properties of real numbers (Copy only if necessary) Reflexive Property

For any number a, a = a Symmetric Property

For any numbers a and b, if a = b, then b = a Transitive Property

For any numbers a, b and c, if a = b and b = c, then a = c

Addition and Subtraction Properties For any numbers a, b, and c, if a = b, then:

a + c = b + c and a – c = b – c Multiplication and Division Properties

For any numbers a, b, and c, if a = b, thena c = b c, and (if c ≠ 0), a/c = b/c

Substitution Property For any numbers a and b, if a = b, then a may be

replaced by b in any equation

2-2: Segments & Properties of Real Numbers

EQUATION: A statement that includes the symbol = Example: If QS = 29 and QT = 52, find ST

QS + ST = QT Definition of Betweenness 29 + ST = 52 Substitution Property 29 + ST – 29 = 52 – 29 Subtraction Property ST = 23 Substitution Property

Using the line above. If PR = 27 and PT = 73, find RT.

P Q R S T

46

2-2: Segments & Properties of Real Numbers

Measurements are composed of two parts: the measure and the unit of measure. The measurement of a segment is also called the length of a segment.

Example in class of using a ruler PRECISION: depends on the smallest unit of

measure being used. GREATEST POSSIBLE ERROR: half the

smallest unit used to make the measurement. PERCENT OF ERROR:

greatest possible errorpercent of error = x 100%

measurement

2-2: Segments & Properties of Real Numbers

Percent Error example using cm Measurement 5.7 cm (57 mm) Precision: 1 mm Greatest Possible Error: 0.5 mm Percent of Error:

Percent Error example using in Measurement: 2 ¼ in (2.25 in) Precision: 1/16 in (0.03125 in) Greatest Possible Error: 1/32 in Percent of Error:

.5100% .88%

57

.03125100% 1.39%

2.25

2-2: Segments & Properties of Real Numbers

Assignment Worksheet #2-2 Additionally, for problems 11-14, calculate

the percent error (both in and cm)