Family Math Studio
Lesson 9.3 · Session 26.AT.11
Write Equations to Represent Relationships Between Two Variables
Write an equation for a situation with a rate that multiplies and a start amount that adds.
NameDate
Tonight's spark
A parking garage charges $5 to drive in, plus $2 for each hour. A driver parks for 3 hours. How much does the driver pay?
Guess first: is it more than $10, or less?
Try it
Work it out on paper. Write one answer on each line.
A taxi charges $2 for each mile. Which equation gives the cost c for m miles?
- A. c = m + 2
- B. m = 2c
- C. c = 2 − m
- D. c = 2m
My answer
Which equation matches '$5 to start plus $2 per hour' with total y for x hours?
- A. y = 7x
- B. y = 2x + 5
- C. y = 5x + 2
- D. y = x + 7
My answer
In y = 2x + 5, what is y when x = 3?
- A. 30
- B. 10
- C. 11
- D. 16
My answer
In y = 2x + 5, which part is the starting amount?
- A. 5
- B. 2
- C. x
- D. y
My answer
A club costs $16 per hour, so c = 16h. How much does it cost for 3 hours?
- A. $19
- B. $48
- C. $13
- D. $163
My answer
Talk about it
Which part of your equation multiplies and which part is added once? How do you know?
Home mission
Pretend a parking spot costs $5 to enter plus $2 for each hour. Ask your student for the cost of 4 hours. Which number is paid once, and which number repeats?
If we get stuck, ask
- Which amount happens every time, and which happens once?
- Does the rate multiply the variable, or get added to it?
- Test your equation on one row you already know.