Josh and Arobindo create a number line to model the growth of mold on a pizza slice. They estimate when the pizza will have 50 grams of mold, and mark this in on their number line.
Episode Supports
Students’ Conceptual Challenges
Some students might need more time than Josh and Arobindo to recognize or modify a method for finding a more precise time for when the pizza has 50 grams of mold. Students might not realize that the exponential equation y = 3x can suggest a general method using guess and check to narrow in on an exact time.
Focus Questions
For use in a classroom, pause the video and ask these questions:
[Pause the video at 1:06] Why do you think Arobindo argues that the time at which the pizza has 50 grams of mold is greater than 3.5 but less than 4 hours?
[Pause the video at 2:08] How can you use the equation Josh and Arobindo have written and a guess-and-check method to find a more precise time for when the pizza has 50 grams of mold on it?
Supporting Dialogue
Ask your students to summarize Arobindo and Josh’s approach to finding the exact time at which the pizza has 50 grams of mold on it. Ask them to compare that approach with their own ideas for finding that time. How did Josh and Arobindo utilize the equation y = 3x to help them find that time? Ask your students to discuss if this method would always work and any shortcomings they see with this method.
