LESSON
2.2 Constant Rates of Change
How can you identify and represent proportional
relationships?
ADDITIONAL EXAMPLE 1
Randall earns money fixing computers. Is the
relationship between the amount Randall earns and
the number of days a proportional relationship?
Yes; the constant rate of change is $175 per day.
ADDITIONAL EXAMPLE 2
Two pounds of peaches cost $4.50, 5 pounds cost
$11.25, and 10 pounds cost $22.50. Show that the
relationship between the number of pounds of
peaches and the cost is a proportional relationship.
Then write an equation for the relationship.
2.2 LESSON QUIZ
7.4.A
Craig earns extra money as a lifeguard. He earns
$37 for 4 hours and $64.75 for 7 hours.
1. Explain how you know whether the
relationship between earnings and time is a
proportional relationship.
Both rates have the same unit rate, $9.25
per hour.
Craig earns extra money as a lifeguard. He earns
$37 for 4 hours and $64.75 for 7 hours.
2. Identify the constant of proportionality, and
write an equation for the proportional
relationship.
9.25; If y = earnings and x = hours,
= 9.25.
3. Write an equation for the following proportional
relationship.
= 7.5.
How can you identify and represent proportional
relationships?
A proportional relationship will have a rate of
change that is constant between any two
quantities. Find the constant of proportionality,
k, and use it to express the relationship as an
equation in the form = k.