You and Emma might have forgotten to tare the balance with the plastic bag in place.

Dr. Smith: ‘I understand that some of you suspected that the issue might be forgetting to press tare. So, let’s check’.

She directs the students’ attention to the balance’s control panel. “First, I noticed we did zero the scale before adding the fertilizer, so it’s clear we didn’t forget to tare. You can confirm this by checking the display—it should read zero with just the bag on the pan.”

We still have two options to consider. Which is more likely?