SAT Math: Geometry

Coordinate Geometry

If a certain line segment has an endpoint at (3, 5) and an endpoint at (7, 13), what is the midpoint of this line segment?

A. (5, 8)

B. (5, 9)

C. (6, 6)

D. (6, 10)

E. (10, 18)


Knowsys Method

Read the question carefully.  This question does not label the points, so you want to be sure that you do not get them confused.

Identify the bottom line.  Midpoint = ?

Assess your options.  Maybe you have forgotten the midpoint formula.  No worries!  This problem is still easy to solve.  You could draw the line on a coordinate grid and then plot the answer choices, but that will take way too long and might not be very accurate.  Instead, think logically about the midpoint.  It must be the middle between the two x values and the middle between the two y values.  All that you have to do is find the average of each! 

Attack the problem.  What is the average of the x values, which are 3 and 7?  If you add them up you get 10.  10 divided by 2 is 5.  The x value must be 5.

What is the average of the y values, which are 5 and 13?  If you add them up you get 18.  18 divided by 2 is 9.  The y value must be 9.

The midpoint that you found is located at (5, 9). 

Loop back.  You solved for your bottom line, so all you need to do is select your answer!

The correct answer is (B).

This is an easy question.


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