## Wednesday, March 02, 2011

### Algebra/Basics Review in Geometry

I'm basically teaching two levels of geometry this year even though we call them both "preAP". I have the 8th and 9th graders in one class, and for the most part they whiz through everything and delight in the challenging problems. I'm also teaching 10th graders that are in other sections, and they approach math in a different way. I have to keep reminding myself not to rush rush rush through topics and to keep remembering that they need more practice on everything to make it stick and to make it make sense.

I am doing one thing, though, to help them keep their algebra skills fresh: ALGEBRA :). For example, for the last few topics, I made sure to make up geometry problems that ended up having a factorable quadratic equation in it at some point. This led us to recall FOILing and ("claw"ing .... Thanks, Mrs. H) and factoring. Now I'm making sure to include quadratics that CAN'T be factored (hello quadratic formula review).

BUT. Here are some things that I didn't think would come up, but did/do, and REALLY I should make a mental (or better) note to myself of where things can go askew, so that I can make more problems throughout the year to have such examples, so that we can have a discussion about them and keep them fresh in our minds.

Example 1:

A student is solving: 2x + 4 = (1/2)x + 8, for example.
Hmmmm, I don't like that (1/2)x,
so I'll just remember that I can do the opposite to x to undo it,
and I multiply ONLY the 2x and the (1/2)x by 2 to end up with:
4x + 4 = x + 8. Eeeeek.

Example 2:
A student gets to a point in an equation where they have (13/2)x = 14. Well, heaven forbid we keep things in fractions and go the easier route of multiplying both sides by 2/13 to get x = 28/13. Boom. Done.
No.
We convert to 6.5x = 14.
We stress that 14 is not easily divided by 6.5.
We chug through and do long division and create pain and suffering for ourselves.
We curse the teacher for such a hard problem and no calculator.

Example 3:
Teacher takes the expedient route frequently and makes up problems where the answers are integers. This saves time, she thinks, so that they're not struggling with messy things and they're concentrating on new material.
Students freak out the first instance an answer is not integer.
Gasp! I must have done something wrong. Things ALWAYS work out nice and pretty in "math world". Fractions are not REAL numbers, no matter WHAT my teacher says. Oh, and by the way, "your answer key says 3/2. Is it okay if I write it as 1.5? As 1 1/2?"

Example 4:
A problem comes up where you're asked to find the height of a person. The decimal answer is 4.666666666 feet. You think this either means 4' 6" or 4' 7" (if you round). You DON'T think that 2/3 of a foot is not either of these answers.