SAT Math : How to find slope of a line

Study concepts, example questions & explanations for SAT Math

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Example Questions

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Example Question #511 : Geometry

A line passes through the origin, and the points (1, k) and (k,4). What is a possible value for k?

Possible Answers:

Correct answer:

Explanation:

To find k, first identify what is known.

The origin means the point (0,0).

Therefore the line passes through the points:

Since a line by definition has the same slope between the points, calculation the slope between the origin and each of the points.

Let

therefore the slope is,

Now let,

thus the slope is,

From here set the slopes equal to each other and solve for k.

Multiply by k on both sides.

Example Question #126 : Coordinate Geometry

Axes

Figure NOT drawn to scale

On the coordinate axes shown above, the shaded triangle has area 60. 

Give the slope of the line that includes the hypotenuse of the triangle. 

Possible Answers:

Correct answer:

Explanation:

The length of the vertical leg of the triangle is the distance from the origin  to , which is 12.

The area of a right triangle is half the product of the lengths of its legs  and , so, setting  and  and solving for :

Since this is the positive horizontal distance from the origin, this is also the -coordinate of the -intercept of the line - that is, the line has -intercept .

The slope of a line, given the intercepts , is 

,

Substitute  and :

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