Last week I wondered about why students scoring poorly on the NECAP math did especially poorly on this question:
A real-estate agent received a 3.5% commission on the sale of a house that costs $200,000. What is the amount, in dollars, of the commission? [commission = sale price x rate]
I very obliquely followed that up with a suggestion that maybe it is really a vocabulary/general knowledge problem a la E.D. Hirsch. If you aren't really sure what a commission or real estate agent is, or what the "rate" refers to in the question, you're going to have problems. And that is probably the case for some kids (especially recent immigrants, etc.).
The problem with this interpretation is that the reading scores have proven both higher in general and much easier to improve than the math scores, so it seems unlikely that the difficulty of the math NECAP is due to reading issues.
I was also wondering if for some kids the answer -- a real estate agent would get $7,000 for selling a house -- would not seem plausible, since $7,000 could easily be two or three months income for the student's family (or more) for what might seem like a day or two of work by the agent. How long does it take to sell a house and how many does an agent sell a year? Do you even know?
Regardless, actual math teacher Jonathan jd2718 commented:
Percents. Percents are killers. Ratios are worse. Stick to the algebra, you'll get better results, at least in this country.
OK, I can certainly buy that explanation too. It does illustrate that math is less orderly and sequential than we like to think of it.