Wednesday, March 16, 2011

It isn't what they don't know - it is what they know that isn't so.

It isn't what they don't know - it is what they know that isn't so.

I gave them a problem today that was something like 20(x-3)(x + 3)/(x^2 - 3) - except it wasn't factored.

And they tried to cancel the x^2 from the numerator with the one in the denominator. I kept telling they they couldn't do it - and they argued. (Why would I tell them no? I think I know more math than they do)

Finally I did (5 + 3)/(5 + 4) and showed how you couldn't cancel the 5 and did 3*5/4*5 and showed how you could.

Lord, I am worried about these Juniors - because that is basic.

1 comment:

Mr. W said...

so funny i did a similar example canceling when adding numbers. My students got even more confused. I do so many basic fraction reductions showing each time the operation is multiplication. I still have kids do what your do though. I couldn't tell you which way works better.