Question

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.

Answer 1

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:
\[{c_2} = 35 + 0.10 \times m\]

Answer 2

now we have to know the number m of minute

Answer 3

minutes*

Answer 4

\[c _{1}=20+.15\times1\]
20.15

Answer 5

c1=20+.15*2

20.30

Answer 6

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:
\[\begin{gathered}
{c_1} = {c_2} \hfill \\
20 + 0.15 \times m = 35 + 0.10 \times m \hfill \\
\end{gathered} \]

Answer 7

please solve that equation for m

Answer 8

Can I do a chart

Answer 9

if you want you can do a chart. We can get the answer if we solve that equation for m

Answer 10

\[\Large 20 + 0.15 \times m = 35 + 0.10 \times m\]

Answer 11

C1=20+0.15*3= 20.45
C2=20+0.10*3= 20.330

Answer 12

I mean 20.30

Answer 13

So I have to find the same answer for the same time of minutes

Answer 14

ok! Please substitute m=100, what do you get?

Answer 15

\[\huge c _{1}=20+.15 * 100 = 35\]

Answer 16

and c_2?

Answer 17

\[\huge c _{2}= 35 +.10 * 100=45\]

Answer 18

ok! So they are different again. I think that the solution is m=300. Am I right?

Answer 19

\[\huge c _{1}= 20 + .15*300= 65\]
\[\huge c _{2}=35+.10*300=65\]

Yes, m does equal 300.

Answer 20

perfect! So you can do your chart, using the subsequent values for m:
1, 20, 50, 100, 300 for example

Answer 21

okay thanks

Answer 22

:)