High School

After the journalism club sold 60 magazines, it had [tex]$220[/tex] in profit. After it sold a total of 100 magazines, it had a total of [tex]$420[/tex] in profit. Which equation models the total profit, [tex]y[/tex], based on the number of magazines sold, [tex]x[/tex]?

A. [tex]y + 220 = 2(x + 60)[/tex]
B. [tex]y - 220 = 2(x - 60)[/tex]
C. [tex]y + 220 = 5(x + 60)[/tex]
D. [tex]y - 220 = 5(x - 60)[/tex]

Answer :

Sure! Let's work through the problem step by step to find which equation models the total profit, [tex]\( y \)[/tex], based on the number of magazines sold, [tex]\( x \)[/tex].

We have two data points for the number of magazines sold and their corresponding profit:
1. When 60 magazines are sold, the profit is \[tex]$220.
2. When 100 magazines are sold, the profit is \$[/tex]420.

From these two points, we can determine the linear relationship between the number of magazines sold and the profit.

Step 1: Calculate the slope ([tex]\( m \)[/tex])

The slope of a line ([tex]\( m \)[/tex]) is calculated using the formula:
[tex]\[ m = \frac{{y_2 - y_1}}{{x_2 - x_1}} \][/tex]

In our case:
- [tex]\( x_1 = 60 \)[/tex], [tex]\( y_1 = 220 \)[/tex]
- [tex]\( x_2 = 100 \)[/tex], [tex]\( y_2 = 420 \)[/tex]

Substituting these values into the formula gives:
[tex]\[ m = \frac{{420 - 220}}{{100 - 60}} = \frac{200}{40} = 5 \][/tex]

Step 2: Write the equation in point-slope form

The point-slope form of a line is:
[tex]\[ y - y_1 = m(x - x_1) \][/tex]

Using [tex]\( m = 5 \)[/tex] and the point [tex]\( (x_1, y_1) = (60, 220) \)[/tex], the equation becomes:
[tex]\[ y - 220 = 5(x - 60) \][/tex]

This equation represents the total profit [tex]\( y \)[/tex] based on the number of magazines sold [tex]\( x \)[/tex].

Conclusion:
The correct equation that models the total profit based on the number of magazines sold is:
[tex]\[ y - 220 = 5(x - 60) \][/tex]

Thus, the correct option is D.