How to find the endpoints of a line segment

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SSAT Upper Level Quantitative › How to find the endpoints of a line segment

Questions 1 - 8
1

On the coordinate plane, is the midpoint of and is the midpoint of . has coordinates and has coordinates .

Give the -coordinate of .

Explanation

First, find the -coordinate of . In the part of the midpoint formula

,

set , and solve:

Now, find the -coordinate of similarly, setting

This is the correct response.

2

One endpoint of a line segment on the coordinate plane is the point ; the midpoint of the segment is the point . Give the -coordinate of the other endpoint of the segment.

Explanation

Using the part of the midpoint formula

.

set and solve:

The second endpoint is .

3

On the coordinate plane, is the midpoint of and is the midpoint of . has coordinates and has coordinates .

Give the -coordinate of .

Explanation

First, find the -coordinate of . In the part of the midpoint formula

,

set , and solve:

Now, find the -coordinate of similarly, setting

This is the correct response.

4

On the coordinate plane, is the midpoint of and is the midpoint of . has coordinates and has coordinates .

Give the -coordinate of .

Explanation

First, find the -coordinate of . In the part of the midpoint formula using the coordinates from and

,

set , and solve:

Now, find the -coordinate of similarly, setting

This is the correct response.

5

A line segment on the coordinate plane has midpoint . One of its endpoints is . What is the -coordinate of the other endpoint, in terms of and/or ?

Explanation

Let be the -coordinate of the other endpoint. Since the -coordinate of the midpoint of the segment is the mean of those of the endpoints, we can set up an equation as follows:

6

One endpoint of a line segment on the coordinate plane is the point ; the midpoint of the segment is the point . Give the -coordinate of the other endpoint of the segment.

Explanation

In the part of the midpoint formula

,

set , and solve:

This is the correct -coordinate.

7

On the coordinate plane, is the midpoint of and is the midpoint of . has coordinates and has coordinates .

Give the -coordinate of .

Explanation

First, find the -coordinate of . In the part of the midpoint formula

,

set , and solve:

Now, find the -coordinate of similarly, setting

This is the correct response.

8

A line segment on the coordinate plane has one endpoint at ; its midpoint is . Which of the following gives the -coordinate of its other endpoint in terms of and ?

Explanation

To find the value of the -coordinate of the other endpoint, we will assign the variable . Then, since the -coordinate of the midpoint of the segment is the mean of those of its endpoints, the equation that we can set up is

.

We solve for :

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