Phone Bill Plans
A Linear System By Misha Saini
Allison is in Canada for Christmas break for 2 weeks. Allison is trying to decide which phone company plan to chose to be able to call back home in Brazil. Allison is in search of a plan that is inexpensive if she calls back home 2 times a week for 25 minutes each time. She has the option to chose from either TELUS Mobile or Virgin Mobile. TELUS has a special promotion going on where they charge the customer $0.50 per minute, whereas Virgin is charging $0.10 per minute will additional fixed charge of $26.
Solving the Situation
As seen above in the graph, both plans intersect at coordinates 65, 32.5. Both lines will cross at 65 minutes with cost of $32.50. Below is the graphic equation:
To do so, Allison should first substitute the cost of TELUS's plan (0.50m) into Virgins plan (0.10m + 26).
0.50m = 0.10m + 26
0.50m - 0.10m = 26
0.40m = 26
Allision must divide both sides by 0.40.
0.40m/0.40 = 26/0.40
Therefore, both these plans do intersect at 65 minutes, now Allison must substitute 65 as m.
TELUS plan: C= 0.50(65)
Virgin plan: C= 0.10(65) + 26