Respuesta :

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A.
[tex]1hr \: 15min = 75min[/tex]

[tex]c = 0.22t = 0.22 \times 75 = 16.5[/tex]

cost is $16.50

B.

[tex]26.40 = 0.22 \times t[/tex]

rearrange to solve for t:

[tex]t = \frac{26.40}{0.22} = 120min[/tex]

C. This is the same as part B, only the rate changed

[tex]t = \frac{26.40}{0.25} = 105.6min[/tex]

they ask for the greatest number of minutes, so we round down (take the floor of the value).

the answer is 105 minutes.
mathstudent55
The cost is a function of time in minutes, and t represents minutes.

Part A.

1 hour + 15 minutes = 60 minutes + 15 minutes = 75 minutes

c = 0.22t

For 75 minutes, t = 75

c = 0.22 * 75

c = 16.5

Answer for Part A.: The cost of a 1 hour 15 minute call is $16.50

Part B.

Now we are given the cost, c, and we need to find t, the time in minutes.

c = 0.22t

26.4 = 0.22t

Divide both sides by 0.22

120 = t

t = 120

Answer to Part B.: 120 minutes.

Part C.

The new cost is now 0.25t.
We want the cost to be at most $26.40.
That means the cost must be less than or equal to $26.40.

[tex] 0.25t \le 26.4 [/tex]

[tex] t \le 105.6 [/tex]

The number of minutes must be less than or equal to 105.6 minutes.
Since the calls are charged by whole minutes, the longest call can be 105 minutes.

Answer to Part C.: 105 minutes

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