ACT Math : How to find the slope of a line

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #111 : Coordinate Geometry

What is the slope of line 3 = 8y - 4x?

Possible Answers:

-2

2

0.5

-0.5

Correct answer:

0.5

Explanation:

Solve equation for y. y=mx+b, where m is the slope

Example Question #112 : Coordinate Geometry

If 2x – 4y = 10, what is the slope of the line?

Possible Answers:

–5/2

–2

2

–0.5

0.5

Correct answer:

0.5

Explanation:

First put the equation into slope-intercept form, solving for y: 2x – 4y = 10 → –4y = –2x + 10 → y = 1/2*x – 5/2. So the slope is 1/2.

Example Question #113 : Coordinate Geometry

What is the slope of the line with equation 4x – 16y = 24?

Possible Answers:

1/8

–1/8

–1/4

1/2

1/4

Correct answer:

1/4

Explanation:

The equation of a line is:

y = mx + b, where m is the slope

4x – 16y = 24

–16y = –4x + 24

y = (–4x)/(–16) + 24/(–16)

y = (1/4)x – 1.5

Slope = 1/4

Example Question #114 : Coordinate Geometry

What is the slope of a line which passes through coordinates \dpi{100} \small (3,7)\(\displaystyle \dpi{100} \small (3,7)\) and \dpi{100} \small (4,12)\(\displaystyle \dpi{100} \small (4,12)\)?

Possible Answers:

\dpi{100} \small \frac{1}{2}\(\displaystyle \dpi{100} \small \frac{1}{2}\)

\dpi{100} \small 5\(\displaystyle \dpi{100} \small 5\)

\dpi{100} \small \frac{1}{5}\(\displaystyle \dpi{100} \small \frac{1}{5}\)

\dpi{100} \small 3\(\displaystyle \dpi{100} \small 3\)

\dpi{100} \small 2\(\displaystyle \dpi{100} \small 2\)

Correct answer:

\dpi{100} \small 5\(\displaystyle \dpi{100} \small 5\)

Explanation:

Slope is found by dividing the difference in the \dpi{100} \small y\(\displaystyle \dpi{100} \small y\)-coordinates by the difference in the \dpi{100} \small x\(\displaystyle \dpi{100} \small x\)-coordinates.

\dpi{100} \small \frac{(12-7)}{(4-3)}=\frac{5}{1}=5\(\displaystyle \dpi{100} \small \frac{(12-7)}{(4-3)}=\frac{5}{1}=5\)

Example Question #11 : How To Find The Slope Of A Line

What is the slope of the line represented by the equation 6y-16x=7\(\displaystyle 6y-16x=7\) ?

Possible Answers:

16\(\displaystyle 16\)

\frac{8}{3}\(\displaystyle \frac{8}{3}\)

6\(\displaystyle 6\)

\frac{7}{6}\(\displaystyle \frac{7}{6}\)

-16\(\displaystyle -16\)

Correct answer:

\frac{8}{3}\(\displaystyle \frac{8}{3}\)

Explanation:

To rearrange the equation into a y=mx+b\(\displaystyle y=mx+b\) format, you want to isolate the y\(\displaystyle y\) so that it is the sole variable, without a coefficient, on one side of the equation.

First, add 11x\(\displaystyle 11x\) to both sides to get 6y=7+16x\(\displaystyle 6y=7+16x\) .

Then, divide both sides by 6 to get y=\frac{7+16x}{6}\(\displaystyle y=\frac{7+16x}{6}\) .

If you divide each part of the numerator by 6, you get y=\frac{7}{6}+\frac{16x}{6}\(\displaystyle y=\frac{7}{6}+\frac{16x}{6}\) . This is in a y=b+mx\(\displaystyle y=b+mx\) form, and the m\(\displaystyle m\) is equal to \frac{16}{6}\(\displaystyle \frac{16}{6}\), which is reduced down to \frac{8}{3}\(\displaystyle \frac{8}{3}\) for the correct answer.

Example Question #115 : Coordinate Geometry

What is the slope of the given linear equation?

2x + 4y = -7

Possible Answers:

-2

1/2

-1/2

-7/2

Correct answer:

-1/2

Explanation:

We can convert the given equation into slope-intercept form, y=mx+b, where m is the slope. We get y = (-1/2)x + (-7/2)

Example Question #116 : Coordinate Geometry

What is the slope of the line:

\(\displaystyle \frac{14}{3}x=\frac{1}{6}y-7\)

 

Possible Answers:

\(\displaystyle 28\)

\(\displaystyle -7\)

\(\displaystyle -\frac{1}{28}\)

\(\displaystyle \frac{1}{28}\)

\(\displaystyle -28\)

Correct answer:

\(\displaystyle 28\)

Explanation:

First put the question in slope intercept form (y = mx + b):  

(1/6)y = (14/3)x  7 =>

y = 6(14/3)x  7

y = 28x  7.

The slope is 28.

Example Question #117 : Coordinate Geometry

What is the slope of a line that passes though the coordinates (5,2)\(\displaystyle (5,2)\) and (3,1)\(\displaystyle (3,1)\)?

Possible Answers:

\frac{1}{2}\(\displaystyle \frac{1}{2}\)

\frac{2}{3}\(\displaystyle \frac{2}{3}\)

-\frac{1}{2}\(\displaystyle -\frac{1}{2}\)

-\frac{2}{3}\(\displaystyle -\frac{2}{3}\)

4\(\displaystyle 4\)

Correct answer:

\frac{1}{2}\(\displaystyle \frac{1}{2}\)

Explanation:

The slope is equal to the difference between the y-coordinates divided by the difference between the x-coordinates.

\(\displaystyle m=\frac{y_2-y_1}{x_2-x_1}\)

Use the give points in this formula to calculate the slope.

\(\displaystyle m=\frac{1-2}{3-5}=\frac{-1}{-2}=\frac{1}{2}\)

Example Question #118 : Coordinate Geometry

What is the slope of a line running through points \(\displaystyle (7,3)\) and \(\displaystyle (8,-4)\)?

Possible Answers:

\(\displaystyle \frac{7}{3}\)

\(\displaystyle -7\)

\(\displaystyle -\frac{1}{7}\)

\(\displaystyle 7\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle -7\)

Explanation:

The slope is equal to the difference between the y-coordinates divided by the difference between the x-coordinates.

\(\displaystyle m=\frac{y_2-y_1}{x_2-x_1}\)

Use the give points in this formula to calculate the slope.

\(\displaystyle m=\frac{3-(-4)}{7-8}=\frac{7}{-1}=-7\)

Example Question #4 : How To Find The Slope Of A Line

What is the slope of the line defined as \(\displaystyle 3x + 4y = 22\)?

Possible Answers:

\(\displaystyle \frac{-2}{11}\)

\(\displaystyle \frac{-4}{3}\)

\(\displaystyle \frac{11}{2}\)

\(\displaystyle \frac{-3}{4}\)

\(\displaystyle \frac{4}{3}\)

Correct answer:

\(\displaystyle \frac{-3}{4}\)

Explanation:

\(\displaystyle 3x + 4y = 22\)

To calculate the slope of a line from an equation of the line, the easiest way to proceed is to solve it for \(\displaystyle y\).  This will put it into the format \(\displaystyle y=mx+b\), making it very easy to find the slope \(\displaystyle m\).  For our equation, it is:

\(\displaystyle 4y = 22-3x\) or \(\displaystyle 4y = -3x+22\)

Next you merely need to divide by \(\displaystyle 4\):

\(\displaystyle y = \frac{-3}{4}x+\frac{22}{4}\)

Thus, the slope is \(\displaystyle \frac{-3}{4}\)

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