Answer:
9.) [tex]t=.05m+20[/tex]
10.) [tex]t=.10m+5[/tex]
11.) [tex]300[/tex] minutes of calling would make the two plans equal.
12.) Company B.
Step-by-step explanation:
Let t equal the total cost, and m, minutes.
Set up your models for questions 9 & 10 like this:
total cost = (cost per minute)# of minutes + monthly fee
Substitute your values for #9:
[tex]t=.05m+20[/tex]
Substitute your values for #10:
[tex]t=.10m+5[/tex]
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To find how many minutes of calling would result in an equal total cost, we have to set the two models we just got equal to each other.
[tex].10m+5=.05m+20[/tex]
Let's subtract [tex]5[/tex] from both sides of the equation:
[tex].10m=.05m-15[/tex]
Subtract [tex].05m[/tex] from both sides of the equation:
[tex].05m=15[/tex]
Divide by the coefficient of [tex]m[/tex], in this case: [tex].05[/tex]
[tex]m=300[/tex]
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Let's substitute [tex]200[/tex] minutes into both of our original models from questions 9 & 10 to see which one the person should choose (the cheaper one).
Company A:
[tex]t=.05(200)+20[/tex]
Multiply.
[tex]t=10+20[/tex]
Add.
[tex]t=30[/tex]
Company B:
[tex]t=.10(200)+5[/tex]
Multiply.
[tex]t=20+5[/tex]
Add.
[tex]t=25[/tex]
