The algorithm isn't that bad, but conceptually people absolutely flail at it. You can replicate Liping Ma easily. 1 3/4 ÷ 1/2 was the sample, iirc. Pick a couple of people, ask them to solve, then ask them give you an example that would go with the problem. An appalling number will fail to solve, fail to put in simplest form,or give you a word problem involving multiplication instead of division. |
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9 is really young. He can circle back around years to come.
All the pies and blocks confused me. The shapes and colors took attention away from the numbers themselves. I'd have him compare 1/5 and 3/5 for example. Also divided them using calculator or put them in %. |
23 or 24 US elementary school teachers, chosen among a group specifically interested in math. Some of them were probably teaching younger grades, some of them older. My guess is the ones in upper grades were much more likely to get the right answer, but even they were poor at explanations. She also interviewed a group of Chinese ES math teachers, and they did much, much better. I do wonder to what extent this is still true, IIRC China is moving away from its old Normal School model, and in any case it is a lot richer and more modernized now, and the more bookish men and women may be heading into other parts of the economy. Ma's thesis is that what you want out of math teachers for ES is something she termed "profound understanding of fundamental mathematics". It is an amazing read, one of those books that really did change my thinking. |
I will admit that if I saw that I would not remember how to do that by hand, because it’s been so many years since I had to do it. In would just use my phone calculator if I saw that in real life. I didn’t have any trouble with fractions while in school and I am confident that I could do it easily if I got a quick refresher on the strategy/rule. That’s not the same as not understanding fractions. I am sure there a lot of life science things that I remember from years ago that many other people forget, because I have continued reading about and using that information in my career. I have no use for math most days. |
Flip and multiple! aka imagine you were baking and needed 1.75 cups of flour but only had 1/2 cup measuring cup. You'd figure out you need 3.5 of those 1/2 c scoops (1.75 x 2 divide by 1). |