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

Answer :

To solve this problem, we need to find an equation that models the total profit [tex]\( y \)[/tex] based on the number of magazines sold [tex]\( x \)[/tex].

We have two key pieces of information:
1. When 60 magazines were sold, the profit was [tex]$220.
2. When 100 magazines were sold, the profit was $[/tex]420.

These are two points on a graph: [tex]\((60, 220)\)[/tex] and [tex]\((100, 420)\)[/tex].

### Step 1: Find the Slope

To find the equation of the line, we first calculate the slope [tex]\( m \)[/tex]. The formula for the slope between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is:

[tex]\[ m = \frac{y_2 - y_1}{x_2 - x_1} \][/tex]

Substitute the given values:

[tex]\[ m = \frac{420 - 220}{100 - 60} = \frac{200}{40} = 5 \][/tex]

### Step 2: Use the Point-Slope Form

With the slope [tex]\( m = 5 \)[/tex], we can use the point-slope form of a line equation, which is:

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

Let's use the point [tex]\((60, 220)\)[/tex]:

[tex]\[ y - 220 = 5(x - 60) \][/tex]

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

Thus, the correct equation from the given options is:

A. [tex]\( y - 220 = 5(x - 60) \)[/tex]