ACT Math : ACT Math

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #5 : How To Find The Midpoint Of A Line Segment

What is the midpoint of a real number line with points at \(\displaystyle -7\) and \(\displaystyle 17\)?

Possible Answers:

\(\displaystyle 5\)

\(\displaystyle 10\)

\(\displaystyle 7\)

\(\displaystyle 9\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 5\)

Explanation:

Method A:

To find the midpoint, draw the number line that contains points \(\displaystyle -7\) and \(\displaystyle 17\).  

Mathwarehouse-number-line

Then calculate the distance between the two points.  In this case, the distance between \(\displaystyle -7\) and \(\displaystyle 17\) is \(\displaystyle 24\).  By dividing the distance between the two points by 2, you establish the distance from one point to the midpoint.  Since the midpoint is 12 away from either end, the midpoint is 5.

Mathwarehouse-number-line__1_

 

Method B:

To find the midpoint, use the midpoint formula:

M=\frac{x_{1}+x_{2}}{2}\(\displaystyle M=\frac{x_{1}+x_{2}}{2}\)

M=\frac{-7+17}{2}\(\displaystyle M=\frac{-7+17}{2}\)

M=5\(\displaystyle M=5\)

Example Question #1 : How To Find The Midpoint Of A Line Segment

Janice and Mark work in a city with neatly gridded streets. If Janice works at the intersection of 33rd Street and 7th Avenue, and Mark works at 15th Street and 5th Avenue, how many blocks will they each travel to lunch if they meet at the intersection exactly in between both offices?

 

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 25\)

\(\displaystyle 12\)

\(\displaystyle 9\)

\(\displaystyle 24\)

Correct answer:

\(\displaystyle 10\)

Explanation:

Translating the intersections into points on a graph, Janice works at (33,7) and Mark works at (15,5). The midpoint of these two points is found by taking the average of the x-coordinates and the average of the y-coordinates, giving ((33+15)/2 , (5+7)/2) or (24, 6). Traveling in one direction at a time, the number of blocks from either office to 24th street is 9, and the number of blocks to 6th is 1, for a total of 10 blocks.

 

Example Question #1 : How To Find The Midpoint Of A Line Segment

On the real number line, what is the midpoint between -7\(\displaystyle -7\) and 19\(\displaystyle 19\) ?

Possible Answers:

6\(\displaystyle 6\)

13\(\displaystyle 13\)

-6\(\displaystyle -6\)

2\(\displaystyle 2\)

3\(\displaystyle 3\)

Correct answer:

6\(\displaystyle 6\)

Explanation:

On the number line,-7\(\displaystyle -7\) is 26\(\displaystyle 26\) units away from 19\(\displaystyle 19\).

\(\displaystyle 19-(-7)=26\)

We find the midpoint of this distance by dividing it by 2.

\frac{26}{2}=13\(\displaystyle \frac{26}{2}=13\)

To find the midpoint, we add this value to the smaller number or subtract it from the larger number.

\(\displaystyle -7+13=6\ \text{or}\ 19-13=6\)

The midpoint value will be 6\(\displaystyle 6\).

Example Question #1 : How To Find The Midpoint Of A Line Segment

What is the midpoint between \(\displaystyle (-4, -6)\) and \(\displaystyle (3, 7)\)

Possible Answers:

\(\displaystyle (1,2)\)

\(\displaystyle (1,1)\)

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

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

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

Correct answer:

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

Explanation:

Using the midpoint formula, \(\displaystyle m=(\frac{x_{1}+x_{2}}{2},\frac{y_{1}+y_{2}}{2})\)

 

We get: \(\displaystyle (\frac{-4+3}{2},\frac{-6+7}{2})\)

Which becomes: which becomes \(\displaystyle (-\frac{1}{2},\frac{1}{2})\)

Example Question #10 : How To Find The Midpoint Of A Line Segment

What is the midpoint of a line segment with endpoints \(\displaystyle (3,2)\) and \(\displaystyle (-1,8)\)?

Possible Answers:

\(\displaystyle (11,.5)\)

\(\displaystyle (1,5)\)

\(\displaystyle (2,10)\)

\(\displaystyle (5,7)\)

\(\displaystyle (.5,11)\)

Correct answer:

\(\displaystyle (1,5)\)

Explanation:

The midpoint of a line can be found using the midpoint formula, given by:

\(\displaystyle (x_{m},y_{m}) = \left(\frac{x_{1}+x_{2}}{2},\frac{y_{1}+y_{2}}{2}\right)\)

Thus when we plug in our values we get the midpoint is 

\(\displaystyle \left(\frac{3+-1}{2},\frac{2+8}{2} \right )\)

\(\displaystyle =\left(\frac{2}{2},\frac{10}{2} \right )\)

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

Example Question #14 : Midpoint Formula

What is the midpoint of the line with endpoints:

\(\displaystyle (10,-18)\textup{ and}\)  \(\displaystyle (16,8)\)?

Possible Answers:

\(\displaystyle (-5,10)\)

\(\displaystyle (13,-5)\)

\(\displaystyle (-4,-13)\)

\(\displaystyle (80,-72)\)

\(\displaystyle (26,-10)\)

Correct answer:

\(\displaystyle (13,-5)\)

Explanation:

To find the midpoint given two points, use the formula:

\(\displaystyle (\frac{x_1 +x_2}{2},\frac{y_1 +y_2}{2})\). Thus for our points we see:

\(\displaystyle (\frac{10+16}{2}, \frac{-18+8}{2})\) = \(\displaystyle (13,-5)\)

Example Question #141 : Lines

A line segment has endpoints at \(\displaystyle (1,-4)\) and \(\displaystyle (7,8)\).

What is the midpoint of the line segment?

Possible Answers:

\(\displaystyle (4,2)\)

\(\displaystyle (-2,-4)\)

\(\displaystyle (2,4)\)

\(\displaystyle (2,-4)\)

\(\displaystyle (-4,-2)\)

Correct answer:

\(\displaystyle (4,2)\)

Explanation:

The midpoint can be found by using equations that calculate the values of its x- and y-coordinates. The x-coordinate can be found using the following equation:

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

Likewise, we will calculate the y-coordinate using another formula:

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

These formulas take the average of each coordinate separately in order to calculate the midpoint. In order to solve our question we will substitute in our given values and solve.

\(\displaystyle \left (\frac{x_1+x_2}{2},\frac{y_1+y_2}{2} \right )\)

\(\displaystyle \left (\frac{1+7}{2},\frac{-4+8}{2} \right )=\left (\frac{8}{2},\frac{4}{2} \right )\)

\(\displaystyle \left (\frac{8}{2},\frac{4}{2} \right )=(4,2)\)

Example Question #12 : How To Find The Midpoint Of A Line Segment

A school superintendent is observing bus routes of students using a town map overlaid with a coordinate plane. Two students, Jon and Steve, live on the same street. Their houses correspond to the coordinates of (-3, 4) and (5,8), respectively, on the map. If there is a bus stop exactly between their two houses, what are the coordinates of the bus stop on the map?

Possible Answers:

\(\displaystyle (-1,11)\)

\(\displaystyle (0,0)\)

\(\displaystyle (0,5.5)\)

\(\displaystyle \left(1,6\right)\)

\(\displaystyle \left(-\frac{1}{2},\frac{5}{2}\right)\)

Correct answer:

\(\displaystyle \left(1,6\right)\)

Explanation:

The midpoint formula must be used to find the midpoint of the line segment joining Jon's and Steve's houses. Use the following formula to find the midpoint:

\(\displaystyle \text{Midpoint}=\left(\frac{x_{1}+x_{2}}{2},\frac{y_{1}+y_{2}}{2}\right)\)

In this formula, \(\displaystyle (x_{1},y_{1})\) and \(\displaystyle (x_{2}, y_{2})\) are the coordinates of the students' homes. Substitute in the coordinates of the houses and solve for the midpoint.

\(\displaystyle \text{Midpoint}=\left(\frac{(-3)+5}{2},\frac{4+8}{2}\right)\)

\(\displaystyle \text{Midpoint}=\left(1,6\right)\)

 In this case, the bus stop is at the following coordinate on the town map:

\(\displaystyle \left(1,6\right)\)

Example Question #1 : X And Y Intercept

Find the slope of the following line: 6x – 4= 10

Possible Answers:

5/2

–5/2

1.5

–1.5

Correct answer:

1.5

Explanation:

Putting the equation in y = mx + b form we obtain y = 1.5x – 2.5.

The slope is 1.5.

Example Question #1 : X And Y Intercept

What is the x-intercept of the line in the standard \(\displaystyle \left ( x,y \right )\) coordinate plane for the following equation?

 \(\displaystyle \frac{1}{2}y+10=6x-2\)

Possible Answers:

12

2

3

-24

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

Correct answer:

2

Explanation:

This question is asking us to find the x-intercept. Remember that the y-value is equal to zero at the x-intercept. Substitute zero in for the y-variable in the equation and solve for the x-variable.

\(\displaystyle \frac{1}{2}(0)+10=6x-2\)

\(\displaystyle 10=6x-2\)

Add 2 to both sides of the equation.

\(\displaystyle 10+2=6x-2+2\)

\(\displaystyle 12=6x\)

Divide both sides of the equation by 6.

\(\displaystyle \frac{12}{6}=\frac{6x}{6}\)

\(\displaystyle x=2\)

The line crosses the x-axis at 2. 

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