Question

Acme Phone Card charges $0.10 a minute for each call. Reliable Phone Card charges $0.20 for each call made plus $0.05 a minute. This can be represented by the system of equations shown below, where y is the total cost of the call and x is the length of the call in minutes.

y= 0.1x
y=0.05x+0.2

For what length of the total charges would be the same when using the Acme Phone or the Reliable phone card?

A. 1 1/3 minutes
B. 2 1/2 minutes
C. 3 minutes
D. 4 minutes

Answer 1

The correct answer is D) 4 minutes.

In order to find when they cost the same, we set the equations equal:
0.1x = 0.05x+0.2

Subtract 0.05x from both sides:
0.1x-0.05x = 0.05x+0.2-0.05x
0.05x = 0.2

Divide both sides by 0.05:
0.05x/0.05 = 0.2/0.05
x = 4