📱

Phone Plan Showdown

Analyze and compare mobile phone plans using independent & dependent variables, equations, tables, and graphs.

Unit 9 · Two-Variable Relationships 6.EE.9 Version B
Step 1 of 6
📖

Key Words

Learn these 5 mathematical words before you begin
💾
Independent Variable (x or g)
The quantity that changes independently. In our project, it's the gigabytes of data you use.
g = 5 GB used
💵
Dependent Variable (y or C)
The quantity that depends on the independent variable. Here, it is the total monthly cost.
C = $70 total cost
⚙️
Equation
A mathematical sentence with an equals sign showing how the output is calculated from the input.
C = 10g + 20
📊
Data Table
A structure that lists multiple inputs side-by-side with their corresponding outputs.
5 GB matches $70
📈
Line Graph
A visual model of the relationship. Points are plotted on grid axes and connected with a line.
Coordinates: (5, 70)
✅ Read each key term carefully. When you understand how independent data relates to dependent cost, click Next Step.
📱

Step 1 — Design Your Plan & Equation

Choose a flat monthly fee and a rate per GB, then write the cost equation
Your job: Set the price levels for your custom phone plan. Enter a flat fee (base price) and a rate for each gigabyte of data you use.
📊 Research you need for this step📊 Investigación que necesitas para este paso
📱 T-Mobile — Phone Plans ↗T-Mobile — Planes de teléfono ↗ Find: Monthly price per lineBuscar: Precio mensual por línea 📶 Verizon — Phone Plans ↗Verizon — Planes de teléfono ↗ Find: Base monthly price + per-line cost (m and c)Buscar: Precio base mensual + costo por línea (m y c) 🟢 Mint Mobile — Plans ↗Mint Mobile — Planes ↗ Find: Monthly price for different data tiersBuscar: Precio mensual para distintos niveles de datos
MY PLAN Flat Fee: $0 Data Cost: $0 / GB Equation Structure C Total Cost = 0 Cost per GB g GB Used + 0 Flat Fee C = 0g
🟢 Level 1 tip: Try round, friendly values. For example, choose a $20 flat fee and a $10 cost per GB. Your equation will look like: C = 10g + 20.
LEVEL 2 CHALLENGE
Feel free to pick decimal numbers (e.g. $8.50 per GB, $15 base fee). Write your equation to perfectly model your choices!
Need help writing the equation?

Your equation shows how to find the dependent variable (C) from the independent variable (g). Multiply the rate per GB by g, then add the flat monthly fee.
Example: $10/GB and $20 flat fee → C = 10g + 20.

📊

Step 2 — Generate Your Data Table

Calculate the total monthly cost for different amounts of data
Your job: Calculate the monthly costs for 0 GB, 1 GB, 2 GB, 5 GB, and 10 GB of data based on your step 1 parameters.
Independent Variable: Data (g) 0 GB: Flat fee only 2 GB: 📦 📦 (2 packets) 5 GB: 📦 📦 📦 📦 📦 (5 packets) Dependent Variable: Cost (C) 0 GB → $0.00 2 GB → $0.00 5 GB → $0.00
🟢 Level 1 tip: Multiply the gigabytes (g) by your rate, then add the base flat fee.
LEVEL 2 CHALLENGE
Write down your coordinates as (g, C) ordered pairs in the last column. Example: (5, 70).
Data Used (g GB) Equation Work / Process Total Cost ($ C) Ordered Pair (g, C)
0 GB $0 base fee
1 GB rate × 1 + fee
2 GB rate × 2 + fee
5 GB rate × 5 + fee
10 GB rate × 10 + fee
Need help with calculations?

If your plan is C = 10g + 20:
• For 0 GB: 10(0) + 20 = $20
• For 1 GB: 10(1) + 20 = $30
• For 5 GB: 10(5) + 20 = $70

📈

Step 3 — Graph and Analyze Your Plan

Look at your plan's visual representation and answer coordinate questions
Your job: Examine the line graph generated below and answer the analysis questions.
Data Used (gigabytes, g) Monthly Cost ($)

🌎 Real-World Market Prices

Below are real average competitor prices. Compare your plan's cost for 5 GB of data ($0.00) to these tiers:

Plan Tier Average Price Description
Basic Plan (Limited Data) $15 – $30 / month Includes 2GB to 5GB of data. Best for light users.
Mid-Tier Plan (Standard) $35 – $48 / month Includes 10GB to 15GB of data. Standard family plan.
Unlimited Data Plan $50 – $80 / month Unlimited data, speeds may slow down after 50GB.
👥

Step 4 — Compare with a Partner

Interview a classmate about their plan, graph both, and find the cheaper option
Your job: Enter details from a classmate's phone plan. Compare costs side-by-side using a double-line graph and table.
📊 Research you need for this step📊 Investigación que necesitas para este paso
📊 WhistleOut — Compare Carriers ↗WhistleOut — Compara operadores ↗ Find: Compare two plans' total cost over several monthsBuscar: Compara el costo total de dos planes a lo largo de varios meses

📈 Cost Comparison Table

Data Used (GB) Your Plan Cost Partner's Plan Cost Cheaper Plan
Enter classmate details and click compare.
🏆

Step 5 — Complete and Submit

Write your sales pitch, review the rubric, and download your final report
Your job: Write a pitch explaining why your plan is a great choice. Review your checklist, and generate the final report for your teacher.

✅ Project Checklist

  • I defined the independent and dependent variables.
  • I wrote and validated the correct equation for my plan.
  • I completed and verified my data table.
  • I analyzed the graph (y-intercept and proportionality).
  • I compared my plan with a classmate's plan side-by-side.
  • I wrote a pricing presentation pitch using my real numbers.

📊 Rubric — How You Are Scored

Skill 4 — Expert 3 — Proficient 2 — Developing
Variables & Equation (6.EE.9) Variables defined correctly; equation represents rate and flat fee perfectly. Variables defined; equation matches flat fee and rate correctly. Equation has minor arithmetic or formatting errors.
Data Table Table is 100% correct; process column shows complete step-by-step arithmetic. Table is correct with minor work missing. Multiple calculation errors in costs or ordered pairs.
Line Graph Analysis Intercept, 8GB cost, and proportionality identified correctly with deep conceptual explanations. Correct answers with simple explanations. Incorrect intercept or calculation; struggles with proportionality.
Peer Comparison Side-by-side table correct; detailed explanation of which plan is better under different data limits. Comparison table correct; identifies cheaper plan at 5 GB. Comparison incomplete or has errors.
Pitch & Presentation Uses real mathematical numbers, equation, and graphs to pitch plan logically. Pitch is complete and uses some plan numbers. Pitch is too short or doesn't connect math to real life. 

        


        

          
          
        

      

    


    
    
    

    
    

      

        🔑 Teacher Grading Console
        
      

      

        Calculated dynamically based on student inputs: