A line of best fit predicts an output from an input, but a question can ask you to work backward from the output. If the line’s equation is labeled on the plot, use it instead of fitting the scattered points again. Set the predicted output equal to the target and use a Desmos regression to find the input. A nearby measured dot isn’t the line’s prediction.
Hints
- Hint 1
A prediction comes from the fitted line; a dot records one measured pair. Use the equation printed beside the line, even if a dot looks close to the target speed.
- Hint 2
Rotation speed is the output, while flow rate is the input. Set the line’s predicted rotation speed equal to the target speed. Which variable will you need to solve for?
Step-by-step
Use the labeled line of best fit
Step 1Turn the target speed into an equation
The line is labeled , where (read “y-hat”) means the predicted rotation speed. The question gives a predicted speed of , so use the line, not a nearby measured dot, and set its output to :
- Step 2
Find the flow rate in Desmos
Type . Use for the unknown input and to ask Desmos to find the value that makes the two sides match. Under PARAMETERS, Desmos shows . Since is flow rate, the prediction is approximately liters per minute. Choice C.