ACT Math : Other Lines

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 : How To Find Out If A Point Is On A Line With An Equation

Consider the lines described by the following two equations:

4y = 3x2

 

3y = 4x2

Find the vertical distance between the two lines at the points where x = 6.

Possible Answers:

36

48

44

21

12

Correct answer:

21

Explanation:

Since the vertical coordinates of each point are given by y, solve each equation for y and plug in 6 for x, as follows:

Taking the difference of the resulting -values give the vertical distance between the points (6,27) and (6,48), which is 21.

Example Question #481 : Geometry

For the line

\displaystyle y=\frac{1}{3}x-7

Which one of these coordinates can be found on the line?

Possible Answers:

(3, 7)

(9, 5)

(3, 6)

(6, 12)

(6, 5)

Correct answer:

(3, 6)

Explanation:

To test the coordinates, plug the x-coordinate into the line equation and solve for y.

y = 1/3x -7

Test (3,-6)

y = 1/3(3) – 7 = 1 – 7 = -6   YES!

Test (3,7)

y = 1/3(3) – 7 = 1 – 7 = -6  NO

Test (6,-12)

y = 1/3(6) – 7 = 2 – 7 = -5  NO

Test (6,5)

y = 1/3(6) – 7 = 2 – 7 = -5  NO

Test (9,5)

y = 1/3(9) – 7 = 3 – 7 = -4  NO

Example Question #4 : How To Find Out If A Point Is On A Line With An Equation

Solve the following system of equations:

–2x + 3y = 10

2x + 5y = 6

Possible Answers:

(3, –2)

(2, 2)

(3, 5)

(–2, 2)

(–2, –2)

Correct answer:

(–2, 2)

Explanation:

Since we have –2x and +2x in the equations, it makes sense to add the equations together to give 8y = 16 yielding y = 2.  Then we substitute y = 2 into one of the original equations to get x = –2.  So the solution to the system of equations is (–2, 2)

Example Question #3 : How To Find Out If A Point Is On A Line With An Equation

Which of the following sets of coordinates are on the line y=3x-4\displaystyle y=3x-4?

Possible Answers:

(2,-2)\displaystyle (2,-2)

(1,5)\displaystyle (1,5)

(1,2)\displaystyle (1,2)

(3,4)\displaystyle (3,4)

(2,2)\displaystyle (2,2)

Correct answer:

(2,2)\displaystyle (2,2)

Explanation:

(2,2)\displaystyle (2,2) when plugged in for y\displaystyle y and x\displaystyle x make the linear equation true, therefore those coordinates fall on that line.

y=3x-4\displaystyle y=3x-4

\displaystyle 2=3(2)-4

\displaystyle 2=6-4

\displaystyle 2=2

Because this equation is true, the point must lie on the line. The other given answer choices do not result in true equalities.

Example Question #4 : How To Find Out If A Point Is On A Line With An Equation

Which of the following points can be found on the line \small y=3x+2\displaystyle \small y=3x+2?

Possible Answers:

\displaystyle (-1,2)

\displaystyle (1, 5)

\displaystyle (1, 0)

\displaystyle (2, 7)

\displaystyle (0, 1)

Correct answer:

\displaystyle (1, 5)

Explanation:

We are looking for an ordered pair that makes the given equation true. To solve, plug in the various answer choices to find the true equality.

\displaystyle y=3x+2

\displaystyle 5=3(1)+2

\displaystyle 5=3+2

\displaystyle 5=5

Because this equality is true, we can conclude that the point \displaystyle (1,5) lies on this line. None of the other given answer options will result in a true equality.

Example Question #1 : How To Find Out If A Point Is On A Line With An Equation

Which of the following points is on the line \displaystyle y=15x + 22?

Possible Answers:

\displaystyle (1.5,32)

\displaystyle (6.5,80.5)

\displaystyle (4,104)

\displaystyle (2.5,66)

\displaystyle (5.5,104.5)

Correct answer:

\displaystyle (5.5,104.5)

Explanation:

The only thing that is necessary to solve this question is to see if a given \displaystyle x value will provide you with the \displaystyle y value paired with it. Among the options provided, only \displaystyle (5.5,104.5) works. This is verified by the following simple substitution:

\displaystyle y = 15 * 5.5 + 22

\displaystyle y=104.5

Example Question #83 : Coordinate Plane

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 #84 : Coordinate Plane

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

Possible Answers:

2

–0.5

0.5

–5/2

–2

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 #1411 : Gre Quantitative Reasoning

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

Possible Answers:

–1/4

1/4

1/2

–1/8

1/8

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 #31 : Lines

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

Possible Answers:

\dpi{100} \small \frac{1}{5}

\dpi{100} \small 5

\dpi{100} \small \frac{1}{2}

\dpi{100} \small 3

\dpi{100} \small 2

Correct answer:

\dpi{100} \small 5

Explanation:

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

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

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