1. What plan would cost less for a 10 minute call: Plan A or Plan B?

Set up a table (like the one on the right) to help you answer this question.

(For the teacher)
Use Quick Poll #1
to find out how the students did. Type in: Which plan costs less for a 10 minute call: Plan A or Plan B?



2. Will Plan A ever equal Plan B? Continue your table to find out how long a call you would have to make in order for the plans to charge the same amount.

Use Quick Poll #2 to find out how the students did. Type in: How many minutes would you need to talk in order for Plan A to be the same as Plan B?


3. Will Plan A ever equal Plan B? Continue your table to find out how long a call you would have to make in order for the plans to charge the same amount.

Use Quick Poll #3 to find out how the students did. Type in: How many minutes would you need to talk in order for Plan A to be better than Plan B?


For extra credit (using the graphing calculator):

Write a function equation for each plan.
    • Plan A: _____________________
    • Plan B: _____________________
To enter the equations into the graphing calculator follow the directions below.

Press the [y=] key

In y1= Type in .02x + .75
Press ENTER
In y2= Type  .05x
Press ENTER
Press ZOOM
Highlight 6:ZStandard
Press ENTER

Press WINDOW. Change it so it looks like this:

Press GRAPH. You should see this:

Press ZOOM
Highlight 1:ZBOX
Press ENTER
Note:  a blinking cursor appears on your graph.  Using the cursor keys, position the cursor just to the left of where you think the intersection is.
Press ENTER
Note:  use your right cursor key to drag the cursor to just beyond where you think the intersection is.
Note:  use your down cursor key to drag the cursor just below where you think the intersection is.


Press ENTER

Press 2nd CALC
Highlight 5:intersect
Press ENTER
Note: you’re asked First Curve? It is so;
Press ENTER
Note: Second Curve? It is so;
Press ENTER
Note: At this point you are asked to guess, you can but you don’t have to
Press ENTER

You should see this:


When is Plan A better than Plan B?

When does Plan A equal Plan B?

When is Plan B better than Plan A?