Got it! (Cognitive Accessibility Example)

Posted on August 14, 2018


I can’t find the exact tweet that started the thread, but somebody posted a problem something like this:

There are potatoes.   They’re 99 % water.   There’s 100 Kg of these potatoes. They get dehydrated.   Now the concentration of potato (not water) is 2%.

How much water did we get rid of?

It gave the answer right there as 50 KG.

I didn’t like it.

People discussed it.   I realized that mathematically speaking, I’ve still got 1 KG of “potato” in the second thing and since 1 KG is 2% of 50 KG… yea, their answer was right.

I still didn’t like it.   Anything I have to explain with a formula is not explained.   I rode.

Make a simpler story, I said.  (I’m a story person.  It’s my learning style. Yes, I call it that.)

Joice has green hair.   THe class has 100 students and … 99% of them don’t have green hair.

The next year, the class is smaller.   Joice is 2% of that class.   How many students left?

I tried the problem out on a friend.  Using her culinary thinking she said she *thought* the answer might be 50 but… couldn’t even bring herself to say it.   The JOice in the class thing?  Suddenly it made sense.

It reminded me of Rene Grimes talking about how we may underestimate the cognitive leap from counting quantities to continuous amounts.

And, if this makes more sense to more than two people, it might just be a great example of making a problem cognitively accessible.

I can also make an array of dots displaying that 99% … and yea, I could make a Geogebra THING that would calculate the percents as I peel off teh dots.   When will the 1 green dot be 2 percent?

I had fun contemplating how this would play out in real life as well as with bigger numbers like populations.  (Really.  People want to know why I commute by bike. I can’t do that in the car. CRASH!)

I realized it’s very remotely connected to why it is so hard to get a student out of the first percentile with a skill.   There are just fewer people down there…

Not making the Geogebra thing b/c I have three more blog posts about articles to do…



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