Question

a cell phone service provider charges $20 per month plus $0.05 per minute of phone use. the company uses the following formula to calculate a customers monthly bill

$c = 20+0.05m$, where $c$ = the total cost and $m$ = the number of minutes

if a customer is charged $41.40, how many minutes did the customer use?

22 minutes

428 minutes

428 minutes

508 minutes

Explanation:

Step1: Substitute the value of \(c\) into the formula

Given \(c = 41.40\) and the formula \(c=20 + 0.05m\), we substitute \(c\):
\(41.40=20 + 0.05m\)

Step2: Solve for \(0.05m\)

Subtract \(20\) from both sides of the equation:
\(41.40−20=0.05m\)
\(21.40 = 0.05m\)

Step3: Solve for \(m\)

Divide both sides of the equation by \(0.05\):
\(m=\frac{21.40}{0.05}\)
\(m = 428\)

Answer:

428 minutes