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lizz123

  • one year ago

Medal One cell phone plan charges 20 dollars per month plus 0.15 cents per minute used. A second cell phone plan charges 35 dollars per month plus 0.10 cents per minute used. Find the number of minutes you must talk to have the same cost for both calling plans.

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  1. Michele_Laino
    • one year ago
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    the cost for the first phone is: \[{c_1} = 20 + 0.15 \times m\] where m is the number of minutes. Whereas the cost for the second phone is: \[{c_2} = 35 + 0.10 \times m\]

  2. Michele_Laino
    • one year ago
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    now we have to know the number m of minute

  3. Michele_Laino
    • one year ago
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    minutes*

  4. lizz123
    • one year ago
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    \[c _{1}=20+.15\times1\] 20.15

  5. lizz123
    • one year ago
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    c1=20+.15*2 20.30

  6. Michele_Laino
    • one year ago
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    yes! nevertheless we have to find the value of m. In order to that we see that the cost c_1 is equal to the cost c_2 when the subsequent equation holds: \[\begin{gathered} {c_1} = {c_2} \hfill \\ 20 + 0.15 \times m = 35 + 0.10 \times m \hfill \\ \end{gathered} \]

  7. Michele_Laino
    • one year ago
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    please solve that equation for m

  8. lizz123
    • one year ago
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    Can I do a chart

  9. Michele_Laino
    • one year ago
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    if you want you can do a chart. We can get the answer if we solve that equation for m

  10. Michele_Laino
    • one year ago
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    \[\Large 20 + 0.15 \times m = 35 + 0.10 \times m\]

  11. lizz123
    • one year ago
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    C1=20+0.15*3= 20.45 C2=20+0.10*3= 20.330

  12. lizz123
    • one year ago
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    I mean 20.30

  13. lizz123
    • one year ago
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    So I have to find the same answer for the same time of minutes

  14. Michele_Laino
    • one year ago
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    ok! Please substitute m=100, what do you get?

  15. lizz123
    • one year ago
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    \[\huge c _{1}=20+.15 * 100 = 35\]

  16. Michele_Laino
    • one year ago
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    and c_2?

  17. lizz123
    • one year ago
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    \[\huge c _{2}= 35 +.10 * 100=45\]

  18. Michele_Laino
    • one year ago
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    ok! So they are different again. I think that the solution is m=300. Am I right?

  19. lizz123
    • one year ago
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    \[\huge c _{1}= 20 + .15*300= 65\] \[\huge c _{2}=35+.10*300=65\] Yes, m does equal 300.

  20. Michele_Laino
    • one year ago
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    perfect! So you can do your chart, using the subsequent values for m: 1, 20, 50, 100, 300 for example

  21. lizz123
    • one year ago
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    okay thanks

  22. Michele_Laino
    • one year ago
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    :)

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