Solve the problem.

-When making a telephone call using a calling card, a call lasting 3 minutes costs $1.25. A call lasting 12 minutes costs $3.50. Let y be the cost of making a call lasting x minutes using a calling
Card. Write a linear equation that models the cost of making a call (y) lasting x minutes.
A) $y = - 0.25 x + 2$
B) $y = 0.25 x + 0.5$
C) $y = 0.25 x - 8.5$
D) $y = 4 x - \frac { 43 } { 4 }$

Question

Solve the problem.

-When making a telephone call using a calling card, a call lasting 3 minutes costs $1.25. A call lasting 12 minutes costs $3.50. Let y be the cost of making a call lasting x minutes using a calling
Card. Write a linear equation that models the cost of making a call (y) lasting x minutes. 
A) $y = - 0.25 x + 2$
B) $y = 0.25 x + 0.5$
C) $y = 0.25 x - 8.5$
D) $y = 4 x - \frac { 43 } { 4 }$

Quizplus · Accepted Answer

To find the correct linear equation, we can use the given information to determine the slope and y-intercept. The slope (m) is the change in cost per minute, which can be calculated as $\frac{\Delta y}{\Delta x} = \frac{3.50 - 1.25}{12 - 3} = \frac{2.25}{9} = 0.25$. To find the y-intercept (b), we can use one of the points, for example, (3, 1.25), and the slope in the equation $y = mx + b$. Substituting gives $1.25 = 0.25(3) + b$, solving for b gives $b = 0.5$. Therefore, the equation is $y = 0.25x + 0.5$.

Solve the Problem y=−0.25x+2y = - 0.25 x + 2y=−0.25x+2 B) y=0.25x+0.5y = 0.25 x + 0.5y=0.25x+0.5

Solve the Problem $y = - 0.25 x + 2$ B) $y = 0.25 x + 0.5$