I made an observation that many students were making a mistake in one problem that they weren't making in the next problem. So I tweeted about it.
It's astounding how many kids are making this mistake (or -3) in #3 but doing #4 just fine. @mpershan #mathmistakes pic.twitter.com/FEemgRRbcX— Tina Cardone (@crstn85) October 20, 2015
And because my online math community is spectacular, I got some feedback.
Inspired by this conversation, I did an experiment last Thursday. I gave students these two problems for a My Favorite No (without talking to them about the test first). The results weren't good, but they weren't particularly consistent either. This is what happened:
- 8 and + 3 (3 students)
+ 8 and + 3
- 8 and *3
*8 and *3
*8 and *(-3)
Dropped the 8 entirely, *3
- 8 and dropped 3
*(-8) and incomplete (3 students)
both incomplete (2 students)