I saw this online a couple years ago, and saved the image. It was posted on Stack Exchange as
A “simple” 3rd grade problem…or is it? by the member with username Enigma.
What’s disturbing here is that the student got the question right. And I suspect many, or most of the students produced the same wrong answer the teacher expected. Do you see the issue?

If I were the student…. pause, I am 50+, but I remember grade school vividly. The school I went to did not have teachers for single subjects. Up till 8th grade, it was one teacher all day. Math was my passion, but not hers. I learned how to politely point out errors, made by either teacher or the published materials we used. Now, the clarifying moment  would come by asking the teacher to continue the chart she produced. “5=1 pieces”? No, you don’t cut for 5 minutes for 1 piece. It’s there at 0 time.

• 0 min = 1 piece
• 10 min = 2 pieces
• 20 min = 3 pieces

The source of this misunderstanding is twofold, the 10 minutes is one cut, it’s the same time to go from 5 pieces to 6. Second, the teacher should not have insisted, but should have used further analysis as I did to better understand the relationship between variables.