standard_description: Use variables to represent two quantities in a real-world problem that change in relationship to one another; write an equation to express one quantity, thought of as the dependent variable, in terms of the other quantity, thought of as the independent variable. Analyze the relationship between the dependent and independent variables using graphs and tables, and relate these to the equation. For example, in a problem involving motion at constant speed, list and graph ordered pairs of distances and times, and write the equation d = 65t to represent the relationship between distance and time.
problem_activity: Task
2 bottles of water cost $5.00.
Fill in the table that shows the costs for 4, 6, and 8 bottles. Find the cost for a single bottle in each case.
| Number of bottles | Cost (\$) | Cost per bottle |
|-------------------|-----------|-----------------|
|       $$2$$       |   $$5$$   |                 |
|       $$4$$       |           |                 |
|       $$6$$       |           |                 |
|       $$8$$       |           |                 |
5 granola bars cost $4.00
Fill in the table that shows the costs for 10, 15, and 20 granola bars. Find the cost for a single granola bar in each case.
| Number of granola bars | Cost (\$) | Cost per bar |
|------------------------|-----------|--------------|
|         $$5$$          |   $$4$$   |              |
|         $$10$$         |           |              |
|         $$15$$         |           |              |
|         $$20$$         |           |              |
Explain why if you can buy $a$ items for $b$ dollars, or buy $2a$ items for $2b$ dollars, the cost per item is the same in either case.


aligns: no