As Math teachers we’re encouraged to make connections between the math we teach and real life. This is good.
But not always. As Math teachers we really should make sure we understand the connections we are making. As shown in this picture from failblog.org (sent to me by Mr. Gearhead). So, the math is right but the interpretation is wrong. Proportionally speaking, if 2 of something takes 2 minutes then 3 of that same thing takes 15 minutes.
What the student realized, and the teacher didn’t, is that to saw a board into two pieces, it takes one cut. To saw a board into three pieces it takes only two cuts. So, 1 cut = 10 minutes, 2 cuts = 20 minutes. The student is correct.
Taking it one step further (or back) according to the teacher’s math, it would take 5 minutes to not cut a board at all (1 piece).
Some people may think “Stupid teacher doesn’t even know their own subject.” But they do know math, they just are clueless when it comes to carpentry.
I can only hope the student took the time to explain their thinking to the teacher, and that the teacher was willing to accept and admit their mistake.