Question 447762
Two cell phone companies are advertising rates.
 Company A charges a rate of $20 per month plus $0.05 per minute.
 Company B charges a rate of $10 per month plus $0.10 per minute.
 What is the number of minutes used above which Company A costs more than Company B?
:
Let m = no. of minutes for this to be true
:
Write an cost equation for each plan
:
"Company A charges a rate of $20 per month plus $0.05 per minute."
Cost A = .05m + 20
:
"Company B charges a rate of $10 per month plus $0.10 per minute."
Cost B = .10m + 10
:
What is the number of minutes used above which Company A costs more than Company B?
Cost A > Cost B
which is
.05m + 20 > .10m + 10
.05m - .10m > 10 - 20
-.05m > -10
We need to get rid of the negatives, multiply by -1, this reverses the inequality sign
.05m < 10
m < {{{10/.05}}}
m < 200
We can translate this to the statement
"Plan A cost more than Plan B when you use less than 200 min"
or
"Plan A cost less than Plan B when you exceed 200 min"
:
Let's see if that is true:
If you use 201 min
A = .05(201) + 20 = $30.05
B + .10(201) + 10 = $30.10