Constant rate of change
Key notes:
The rate of change is equal to the slope.
slope = change in y / change in x
Learn with an example
📍 This graph shows how the amount of time that a receptionist named Colette spends on the phone is related to the number of phone calls she routes to employees.
What is the rate of change?
Write your answer as a decimal or integer.
______ minutes per phone call
Find any two points on the line.
Two points on the line are (0, 30) and (40, 60). Put those points into the slope formula.
slope = change in y / change in x
= 60 – 30 / 40 – 0 Plug in (0, 30) and (40, 60)
= 30 / 40 Subtract
= 3/4 Subtract
= 0.75 Write as a decimal
The slope is 0.75. The rate of change is 0.75 minutes per phone call.
📍 This graph shows how the number of cakes Donald can bake is related to the number of additional sticks of butter he buys.
What is the rate of change?
Write your answer as a decimal or integer.
_______ cakes per stick of butter
Find any two points on the line.
Two points on the line are (0, 3) and (1, 5). Put those points into the slope formula.
slope = change in y / change in x
= 5 – 3 / 1 – 0 Plug in (0, 3) and (1, 5)
= 2/1 Subtract
= 2 Subtract
The slope is 2. The rate of change is 2 cakes per stick of butter.
📍 This graph shows how the amount of time that a receptionist named Danny spends on the phone is related to the number of phone calls he routes to employees.
What is the rate of change?
Write your answer as a decimal or integer.
_________ minutes per phone call
Find any two points on the line.
Two points on the line are (0, 3) and (5, 4). Put those points into the slope formula.
slope = change in y / change in x
= 4 – 3 / 5 – 0 Plug in (0, 3) and (5, 4)
= 1/5 Subtract
= 0 . 2 Write as a decimal
The slope is 0.2. The rate of change is 0.20 minutes per phone call.
let’s practice! 🖊️
