Question

Emma wants to compare some cell phone plans by graphing their cost per text message. Mobilama charges a flat rate of $30 for unlimited texts. Celly-On-The-Go has no set-up charge, but it does charge $0.10 per text. Ringit Wireless only charges $0.05 per text, but it has an account charge of $15.

Explain to Emma how she can graph these cell phone plans and, describe what key features of the graphs she should consider when making a decision.

Answer 1

@iambatman
@texaschic101
@zepdrix
@Ashleyisakitty
@radar

Answer 2

@Loser66

Answer 3

Hey c:

Answer 4

Hey

Answer 5

So let's ummmm, make some linear equations for these different cellphone plans.
Our independent variable, \(\Large\rm x\), will be the number of text messages made,
while our dependent variable, \(\Large\rm y\), will be the cost of the plan.
(The cost depends on the number of texts you send/recieve).

Answer 6

Again, these are linear, so we'll have functions of the form:\[\Large\rm y=mx+b\]

Answer 7

The first company, `Mobilama`, charges $30 no matter how many text messages you make.
\(\Large\rm y=mx+30\)
And our slope value, the cost per text message will be 0,
\(\Large\rm y=30\)
We only pay an up front cost of $30.
That one make sense? :o

Answer 8

OHOHO i see

Answer 9

I plugged zero in for m.

Answer 10

`Celly-On-The-Go` charges NO up front cost,
but charges 0.10 per text message.
\(\Large\rm y=.10x+0\)

Answer 11

How bout the third one, you wanna give that a shot? :D

Answer 12

y=.1

Answer 13

Hmm your x disappeared from the equation D: That's strange.
If you include the x, then yes, that's the correct simplification for the second one.

Maybe we should use subscripts to keep track of these or something 0_o
\(\Large\rm y_m=30\) <--- Mobilama's plan
\(\Large\rm y_c=.1x\) <--- Celly-On-The-Go's plan
\(\Large\rm y_r=?\)

How bout the third one?
Can you come up with an equation for Ringit Wireless?

Answer 14

hm do so we pay only 10

Answer 15

wait oops sorry wrong thing

Answer 16

y=.05x+0

Answer 17

Ok you have part of the equation correct.
"Ringit Wireless only charges `$0.05 per text`, but it has an `account charge of $15`."
Since we're calling x the number of text messages, here is what we get for the total charge due to text messages.
\[\Large\rm y_r=.05x+\]What about the other piece of information though?
It's not 0 for the account charge / up front cost.

Answer 18

.05+15

Answer 19

.05x+15

Answer 20

\[\Large\rm y_r=.05x+15\]Ok great \c:/

Answer 21

So graphing...

Answer 22

Labeling our graph is very important.

Answer 23

i cant fit that in my test

Answer 24

Oh oh I see, you're just supposed to "explain" how to graph? My bad.

Answer 25

Tell Emma to label her axes:
`Number of text messages along the x-axis`
`Total cost along the y-axis`

Important features:
`When you send zero text messages, compare the costs`
So that means, when x=0, explain which one costs the most.
Ummm what else...
That's prolly enough info :d Blah I dunno

Answer 26

Oh she wants to make a decision based on the information.
So maybe figure out when each plan offers the best deal.

Answer 27

Here is a graph of all three plans:
https://www.desmos.com/calculator/bmand9v2nr
it might help you to visualize it better.

Answer 28

It looks like Celly-On-The-Go offers the best deal (lowest price, blue line) if Emma decides to use less than 300 texts.

Answer 29

If she plans on using more than 300 minutes, she should go for Mobilama, see how the red line is lowest after 300?

Answer 30

oh k thx and can you help with 1-2 more please?

Answer 31

Ok Emma, I went to desmo's and graphed them so I could get a better visual. The type of graph is a line graph, and its pretty simple. Each plan has t's own function, Mobilama's graph function is y=30. There's no change. Celly-On-The-Go starts at zero,but continues to increase for every text and ends up being the most expensive. y=.1. Ringit Wireless is the middle line, and it is represented by y=.05+15. 15 of course being the y intercept, and represents the initial cost of the account.