The students find a logarithmic expression that is equivalent to log3 (x) + log3 (y). They explain what their equation means in terms of the moldy food context and justify their proposed relationship using a number line.
Episode Supports
Focus Questions
For use in a classroom, pause the video and ask these questions:
[Pause the video at 0:26] Fill in the blank to make this equation true: log3(x) + log3(y) = log3(__). Justify your choice.
[Pause the video at 2:35] Summarize Arobindo and Josh’s argument for why the logarithmic expressions log3x, log3y, and log3(xy) accurately represent the elapsed time needed for the mold to grow by the factors of x, y, and xy, respectively.
Supporting Dialogue
Pause the video at [1:48] so that students can see the diagram Arobindo and Josh created. Ask your students to analyze the diagram and then explain to a partner how they could use the diagram to explain why log3x + log3y = log3(xy).
