Midpoint 20/21 (Lesson 6.3a)
The midpoint is the point (x, y) that is in the middle.  We can find the midpoint using the midpoint formula:
or you can just take the average of both the x- and y-coordinates you'll add the x-coordinates, then divide by twothen add the y-coordinates and divide by two
m = 
(
x1 + x2
2
,
y1+ y2
2
)
Examples:
1)
2)
A (3, -9)
B (-3, 5)
A(1, 0.8)
B (6, 4)
x-coord = 1 + 6
x-coord = 3 + (-3)
x = 0
M = (3.5, 2.4)
2
= 0
M = (0, -2)
2
2
y-coord = -9 + 5
y-coord = 0.8 + 4
y = -4
2
= -2
2
2
Now it's your turn.  Make sure you write your answers
as integers or decimals....
Make sure you include the parentheses (   ) when writingordered pairs:  Ex:  (5,2) (Some problems already have the parentheses)
Make sure when writing numbers between 0 and 1, you 
begin with 0:   Ex 1/2 = 0.5
Use no spaces between coordinates
No fractions!
Find the midpoint ofsegment AB.
M = (
*Write as decimals, if necessary.
,
)
A
(1, -2)
(5, 1)
B
midpoint coordinates =
*Write as an ordered pair with NO spaces. ex: (0,0)
2)  Find the coordinates     of the midpoint of      segment AB.

A
(-2, 3)
(2, 7)
B
(0.5, -0.5)
(1, -1)
(-1, 1)
(-0.5, 0.5)
What is the midpoint?
A
B
*Write as an ordered pair with NO spaces.  Use decimals if needed.  ex: (5,2.5)
Coordinates of midpoint = 
4)  Given the coordinates for segment CD,      C = (-1, 6) and D = (4, 10).  Find the      coordinates of the midpoint of CD.
5) You can find the midpoint of every line.
(read carefully!)
True
False
Depends on the line.
6) The _________ of a segment is the point that divides
the segment into two congruent segments.
segment addition postulate
line
distance
midpoint
What is the midpoint of Segment AB?
*Write as an ordered pair with NO spaces.  Use decimals if needed.  ex: (5,2.5)
A
B
So, we will add these numbers to the midpoint to find D.
So, let's look at this...
If the midpoint M of segment CD is (3, 2) and C is (-2, 5)
then we just need to find the difference between the
x-coordinates and the y-coordinates.
To find an endpoint, we will look at this without using a
formula.
C(-2, 5)
D (3 + 5, 2 + (-3))
+5
M(3, 2)
Final Answer:  D(8, -1)
C(-2, 5)
-3
M(3, 2)
8) Use the given endpoint R and midpoint M of segmentRS to find the coordinates of the other endpoint S.
R(3,0), M(0,5)
Coordinates of point S:
*Write as an ordered pair with NO spaces.  Use decimals if needed.  ex: (5,2.5)
9) In the diagram, M is the midpoint of the segment.Find AM.
A
AM=
x+7
M
2x
C
0
2
-2
4
-4
6
-6
8
-8
(it's a single number, no ordered pair)
Find the midpoint
A
M = 
B
0
2
-2
4
-4
6
-6
8
-8
If M is the midpoint of Segment AB, then
what is the coordinate of B?
B =
A
M
What is the midpoint of Segment XY?  

X (5, 12)
Y (9, -2)
(14, 10)
(4, 10)
(4, 14)
(7, 5)
Left Over 
A (4, 5)  B (1, -11) 
Match up the midpoints with their endpoints.
(2.5, -3)
?
(4, 2)
?
A (-2, 8)B (-6, 3)
(-4, 5.5)
?
A (-10, 0)B (6, -5)
(-2, -2.5)
?
(5, 1)
?
A (7, 4)B (3, -2)
What are the coordinates of the endpoint T for 
the Segment AT?  M is the midpoint of each.
A(5, -4) and M(1, 2)
A(-1, 8) and M (2, 6)
A(-4, 0) and M(-7, 2)
A(9, 7) and M(2, 3)
A(-7, -2) and M(-8, 3)
T(-3, 8)
?
T(5,4)
?
T(-9, 8)
?
T(-5, -1)
?
T(-10,4)
?
If M is = 3 and Segment AM = 5, what are the possiblecoordinates of A?  Select all that apply
8
-8
-2
cannot be determined
If R = 6 and the midpoint M is = 4, what is the 
coordinate of the other endpoint?
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