Name:______
Talk and Text Plans
A cell phone company offers two talk and text plans. The company charges a monthly service fee of $20 for either plan the customer chooses:
Talk and Text Plan A: 5 cents a minute and twenty dollars for 250 texts.
Talk and Text Plan B: 10 cents a minute (first 100 minutes are free) and fifteen dollars for 200 texts. The equation c = .10(m – 100) + 15 + 20 can be used to represent how much a customer would spend monthly for the minutes used.
a) Express Plan A as an equation where c equals the cost and m equals the minutes used.
b)Graph each Talk and Text Plan to determine when both plans cost the same.
- use graph paper
c)For how many minutes will both plans share the same cost? Use the elimination method to algebraically prove your graph.
d)If a customer has $75 to spend each month, which plan should the customer choose and why? Show your work and justify your answer.
Plan APlan B
e)The company decides to offer a plan c that has unlimited usage for $150. Use the substitution method to determine how many minutes would need to be used with plan B for it to be equivalent to plan C.
Rubric for Talk and Text Plans:
Criteria for student learning (add rows as needed) / 4 / 3 / 2 / 1 / 0Part a – expressing plan as an equation in slope-intercept form / Equation is in slope-intercept form and has correct values for slope and intercept / Equation is in slope-intercept form, but 1 value is incorrect / Equation is in slope-intercept form, but both values are incorrect / Equation is not in slope-intercept form but has at least one value correct / Did not attempt
Part b – Graphing / Two lines are graphed correctly / Two lines are graphed, but only one line is graphed correctly / Two lines graphed with both being incorrect / Only one line graphed / Did not attempt
Part c – Elimination / System is set-up and solved correctly / System is set-up correctly, but a mathematical error was made. / System was partially set-up correctly and the math was done correctly for how the problem was set-up. / System was partially set-up correctly and some of the math was done incorrectly for how the problem was set-up. / Did not attempt
Part d – Selecting a plan and justifying. / Justification matches the work shown and is written using appropriate mathematical terminology and appropriate English grammar / Justification matches the work shown but the response does not use appropriate mathematical terminology and/or appropriate English grammar / Justification partially matches the work shown and the response does not use appropriate mathematical terminology and/or appropriate English grammar / Justification has little support of the work shown and the response does not use appropriate mathematical terminology and/or appropriate English grammar / Did not attempt
Part e – Using Substitution / System is set-up and solved correctly / System is set-up correctly, but a mathematical error was made. / System was partially set-up correctly and the math was done correctly for how the problem was set-up. / System was partially set-up correctly and some of the math was done incorrectly for how the problem was set-up. / Did not attempt