A piece of string is 112 inches long. Cory wants to cut it into two pieces so that one piece is three times as long as the other piece. How long will each piece be?

Responses
A 45 inches and 67 inches45 inches and 67 inches
B 55 inches and 57 inches55 inches and 57 inches
C 28 inches and 84 inches
D 28 inches and 78 inches

11 answers

Let's define the lengths of the two pieces of string:

Let \( x \) be the length of the shorter piece. Then the longer piece will be \( 3x \) (since one piece is three times as long as the other).

According to the problem, the total length of the string is 112 inches. So we can set up the following equation:

\[ x + 3x = 112 \]

Combining like terms, we have:

\[ 4x = 112 \]

Now, we can solve for \( x \):

\[ x = \frac{112}{4} = 28 \]

Thus, the shorter piece is 28 inches long. Now, we can find the longer piece:

\[ 3x = 3 \times 28 = 84 \]

So the longer piece is 84 inches long.

Therefore, the two pieces are 28 inches and 84 inches long.

The correct answer is:

C: 28 inches and 84 inches.

Johnny makes wooden benches to sell. His advertising costs are $150 per month and each bench costs him $100 to make. If he sells each bench for $175, how many benches must he sell to break even each month?
Responses
A 1 bench1 bench
B 2 benches2 benches
C 3 benches3 benches
D 4 benches

To determine how many benches Johnny needs to sell to break even, we'll first calculate his total costs and then compare that to his revenue from selling the benches.

  1. Fixed Costs: Johnny's advertising costs are $150 per month.

  2. Variable Costs: Each bench costs him $100 to make.

  3. Selling Price: Each bench sells for $175.

To break even, Johnny's total revenue from selling benches must equal his total costs.

Let's denote the number of benches sold as \( x \).

Total Costs: \[ \text{Total Costs} = \text{Fixed Costs} + \text{Variable Costs per bench} \times \text{Number of benches} \] \[ \text{Total Costs} = 150 + 100x \]

Total Revenue: \[ \text{Total Revenue} = \text{Selling Price per bench} \times \text{Number of benches} \] \[ \text{Total Revenue} = 175x \]

To break even, we set total costs equal to total revenue:

\[ 150 + 100x = 175x \]

Now, we will solve for \( x \):

  1. Subtract \( 100x \) from both sides: \[ 150 = 175x - 100x \] \[ 150 = 75x \]

  2. Divide both sides by 75: \[ x = \frac{150}{75} = 2 \]

Therefore, Johnny must sell 2 benches to break even each month.

The correct answer is:

B: 2 benches.

A red car is traveling at 55 mph. A blue car is traveling at 65 mph. The cars are 305 miles apart. The cars started at the same spot at different times. The total driving time for the two cars is 5 hours. Which system of equations could be used to solve for the total driving time of the red car (r) and the total driving time of the blue car (b)?
Responses
A r + b = 310
55r = 65b
B r + b = 5
55r + 65b = 305
C r + b = 305
55r + 65b = 5
D 5(r + b) = 120
55r + 65b = 305

To solve the problem, we need to set up a system of equations based on the information given.

  1. Total driving time for both cars: The total driving time for the red car (\( r \)) and the blue car (\( b \)) is 5 hours. \[ r + b = 5 \]

  2. Distance traveled by each car: The red car travels at 55 mph and the blue car travels at 65 mph. We know that the distance traveled by both cars combined must equal the total distance apart (305 miles). The distance can be expressed as: \[ \text{Distance} = \text{Speed} \times \text{Time} \] Therefore, the distance equations for the two cars are:

    • Distance traveled by the red car: \( 55r \)
    • Distance traveled by the blue car: \( 65b \)

    The total distance traveled is: \[ 55r + 65b = 305 \]

So the system of equations we have is:

  1. \( r + b = 5 \)
  2. \( 55r + 65b = 305 \)

Thus, the correct response for the system of equations is:

B: \[ r + b = 5 \ 55r + 65b = 305 \]

x + y = 28

y = 2x - 5

y = Marci; x = Jennifer

Jennifer and Marci are selling cookies for a fundraiser. They sold 28 boxes of cookies together. Marci sold 5 less than twice the number that Jennifer sold. How many boxes of cookies did each girl sell? Use system of equations to solve the problem.
Responses
A Marci sold 11 boxes and Jennifer sold 17 boxes.Marci sold 11 boxes and Jennifer sold 17 boxes.
B Marci sold 13 boxes and Jennifer sold 15 boxes.Marci sold 13 boxes and Jennifer sold 15 boxes.
C Marci sold 15 boxes and Jennifer sold 13 boxes.Marci sold 15 boxes and Jennifer sold 13 boxes.
D Marci sold 17 boxes and Jennifer sold 11 boxes.Marci sold 17 boxes and Jennifer sold 11 boxes.
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To solve the problem using the system of equations provided, we start with:

  1. \( x + y = 28 \) (where \( x \) is the number of boxes Jennifer sold and \( y \) is the number of boxes Marci sold)
  2. \( y = 2x - 5 \) (Marci sold 5 less than twice what Jennifer sold)

Step 1: Substitute the second equation into the first

We can substitute \( y \) from the second equation into the first equation:

\[ x + (2x - 5) = 28 \]

Step 2: Simplify and solve for \( x \)

Combine like terms:

\[ 3x - 5 = 28 \]

Add 5 to both sides:

\[ 3x = 33 \]

Now divide by 3:

\[ x = 11 \]

So, Jennifer sold \( 11 \) boxes of cookies.

Step 3: Solve for \( y \)

Now we can find the value of \( y \) (the number of boxes Marci sold) by substituting \( x \) back into either equation. We'll use the first equation:

\[ y = 28 - x = 28 - 11 = 17 \]

So, Marci sold \( 17 \) boxes of cookies.

Conclusion

Jennifer sold 11 boxes and Marci sold 17 boxes.

Thus, the correct response is:

D: Marci sold 17 boxes and Jennifer sold 11 boxes.

Which of the following system of equations could be perpendicular? Select all that apply.
Responses
y = 3x + 2 and y = 3x + 4
y = 3x + 2 and y = 3x + 4
y = -3x + 4 and y = 1/3x - 2
y = negative 3x + 4 and y = 1 third x negative 2
y = 1/4x + 5 and y = 4x + 3
y = 1 fourth x + 5 and y = 4x + 3
y = - 1/4x + 5 and y = 4x - 3
y = negative 1 fourth x + 5 and y = 4x negative 3
y = -3x + 6 and y = 3x + 2

To determine which equations from the list represent lines that are perpendicular to each other, we need to recall that two lines are perpendicular if the product of their slopes is \(-1\).

In other words, if one line has a slope \(m_1\), then the other line must have a slope \(m_2\) such that:

\[ m_1 \cdot m_2 = -1 \]

Analyzing the Lines:

  1. \(y = 3x + 2\) and \(y = 3x + 4\)

    • Both lines have a slope of \(3\).
    • Since they have the same slope, they are not perpendicular.
  2. \(y = -3x + 4\) and \(y = \frac{1}{3}x - 2\)

    • The slopes are \(-3\) and \(\frac{1}{3}\).
    • Product: \(-3 \times \frac{1}{3} = -1\) (they are perpendicular).
  3. \(y = \frac{1}{4}x + 5\) and \(y = 4x + 3\)

    • The slopes are \(\frac{1}{4}\) and \(4\).
    • Product: \(\frac{1}{4} \times 4 = 1\) (not perpendicular).
  4. \(y = -\frac{1}{4}x + 5\) and \(y = 4x - 3\)

    • The slopes are \(-\frac{1}{4}\) and \(4\).
    • Product: \(-\frac{1}{4} \times 4 = -1\) (they are perpendicular).
  5. \(y = -3x + 6\) and \(y = 3x + 2\)

    • The slopes are \(-3\) and \(3\).
    • Product: \(-3 \times 3 = -9\) (not perpendicular).

Conclusion:

The lines that are perpendicular are:

  • \(y = -3x + 4\) and \(y = \frac{1}{3}x - 2\)

  • \(y = -\frac{1}{4}x + 5\) and \(y = 4x - 3\)

Thus, the correct responses for perpendicular lines are the ones listed above.

The equation for line w, graphed below, is y = - 2/5 x + 4

Create a consistent system of linear equations by graphing a line perpendicular to line w that passes through (1, -8)

To create a system of linear equations consisting of the line \( w \) and a line perpendicular to it that passes through the point \( (1, -8) \), we need to follow these steps:

Step 1: Determine the slope of line \( w \)

The equation of line \( w \) is given as:

\[ y = -\frac{2}{5}x + 4 \]

From this equation, we can see that the slope \( m_w \) of line \( w \) is \( -\frac{2}{5} \).

Step 2: Find the slope of the perpendicular line

The slope of a line that is perpendicular to another is the negative reciprocal of the original slope. Therefore, we calculate the slope \( m_p \) of the perpendicular line:

\[ m_p = -\frac{1}{m_w} = -\frac{1}{-\frac{2}{5}} = \frac{5}{2} \]

Step 3: Write the equation of the perpendicular line

We know the slope \( m_p = \frac{5}{2} \) and it passes through the point \( (1, -8) \). We'll use the point-slope form of the equation of a line:

\[ y - y_1 = m(x - x_1) \]

Substituting in the values:

\[ y - (-8) = \frac{5}{2}(x - 1) \]

This simplifies to:

\[ y + 8 = \frac{5}{2}(x - 1) \]

Now, let's simplify:

  1. Distribute the slope: \[ y + 8 = \frac{5}{2}x - \frac{5}{2} \]

  2. Subtract \( 8 \) from both sides to isolate \( y \): \[ y = \frac{5}{2}x - \frac{5}{2} - 8 \]

  3. Convert \( 8 \) to a fraction with a denominator of 2: \[ 8 = \frac{16}{2} \] So: \[ y = \frac{5}{2}x - \frac{5}{2} - \frac{16}{2} = \frac{5}{2}x - \frac{21}{2} \]

Final equations

The consistent system of linear equations consisting of line \( w \) and the newly formed perpendicular line is:

  1. \( y = -\frac{2}{5}x + 4 \) (line \( w \))
  2. \( y = \frac{5}{2}x - \frac{21}{2} \) (perpendicular line)

Graphing

If you were to graph these two equations:

  • Line \( w \) has a negative slope and crosses the y-axis at \( 4 \).
  • The perpendicular line would rise steeply, with a slope of \( \frac{5}{2} \), and it would cross the y-axis at \( -\frac{21}{2} \) or \( -10.5 \).

This system of equations will be consistent, as they will intersect at a point.