Thursday, February 28, 2008

The REALLY long math problem


The question Beth asked today was, “Why do we have to do multiplication?”

I gave a simple answer, “So when we are at the store and need to buy 10 boxes at 13.76 each we will know how much it will cost”.

She didn’t much care for that answer and said, “I don’t need multiplication for that. I can just do my math” and she explained it quickly.

I didn’t much care for that answer and showed her how it would be done except I used that we would purchase 8 boxes to make it a little more of a problem.

She thought that was too much work and asked, “Why can’t I just do it my way?”

No really understanding “her way”, I asked her to show it to me. Here it is (using 10):

The price is 13.76, so just round it to 14.00.
The 100 is easy.
10 sets of 4 is 40
Change that to 5 sets of 8 by adding the 4’s together
Add 2 of the 8’s twice 16 and 16
That is 32
Left over is the other 8, which she somehow butchered some more that I can’t really remember anymore!!

And she came out with the fact, when rounded, it would be 140.00.

HUH!? Couldn't we have left it rounded in the first place??

1 comment:

Trish said...

Hmmm...Very interesting! Math never was one of my strong subjects...Have fun teaching that one!