by wc
(gresham)
For his phone service, Ryan pays a monthly fee of $13.00, and he pays an additional $0.05 per minute of use. The least he has been charged in a month is $72.45.
What are the possible numbers of minutes he has used his phone in a month?
Use m for the number of minutes, and solve your inequality for m.
Solution
Let m be the number of minutes used.
Monthly cost = fixed cost + variable cost
fixed cost = 13
Variable cost = 0.05 × m
Monthly cost = 13 + 0.05m
It says in the problem that the least he has been charged in a month is $72.45.
This means that the monthly cost is at least 72.45.
In other words, the monthly cost is 72.45 or bigger.
This can be expressed as 13 + 0.05m ≥ 72.45
Just solve the inequality.
13 + 0.05m ≥ 72.45
13 - 13 + 0.05m ≥ 72.45 - 13
0 + 0.05m ≥ 72.45 - 13
0.05m ≥ 59.45
Divide both sides by 0.05
0.05m/ 0.05 ≥ 59.45/0.05
m ≥ 1189
Ryan used at least 1189 minutes
Jul 25, 17 09:06 PM
Learn to solve comparison word problems using modeling
New math lessons
Your email is safe with us. We will only use it to inform you about new math lessons.
Jul 25, 17 09:06 PM
Learn to solve comparison word problems using modeling