The students use their number line and a calculator to determine the amount of time it takes for the mold on the pizza to increase by a factor of 1.5.
Episode Supports
Students’ Conceptual Challenges
Some students may struggle to interpret logarithmic expressions and the result of calculating logarithms. If you notice students struggling with this unproductively, encourage them to represent the mathematics using exponential notation and ask them to make connections between that notation and the logarithmic notation they are just now working with.
Focus Questions
For use in a classroom, pause the video and ask these questions:
[Pause the video at 0:21] How long does it take for the mold to increase by a factor of 1.5?
[Pause the video at 2:36] Josh and Arobindo used logarithms to find the time for the mold to increase by a factor of 1.5. How does the log31.5 relate to the growth factor, and what does the calculated value (0.36) signify?
Supporting Dialogue
Ask your students to share their understanding of how logarithms (in base three) were used by Arobindo and Josh to calculate the amount of time for the mold to increase by a factor of 1.5. How do logarithms help model exponential growth, and what insights does logarithmic notation provide into the context of the moldy pizza?
