Wednesday, August 13, 2014

Currency conversion and 1001 nights

who: J1 (and a bit of J2)
where: bedroom
when: bedtime (particularly after lights out)
what materials: internet connection (not really necessary)

This is another Talking Math With Your Kids -style conversation.

  • J1: Daddy, what's 100 pounds (British pounds) in Baht (Thai currency)?
some discussion about which way he wanted to convert as I hadn't really been listening
  • D: Well, there are about 50 baht per pound.
  • J1: So, I need 50 groups of .  . .can you use the computer to calculate it?
  • D: Yes, I can, but we don't need to.  First, though, we need to figure out what calculation to do. You said you have 100 pounds and there are about 50 baht per pound
some mumbling, not really getting anywhere; I'm tempted to comment and guide, but hold back.
  • J1: I have 100 groups of 50.  What's that?
  • D: What about 10 pounds in baht?
  • J1: (pause) that's 500
  • D: how did you calculate that?
I was assuming some strategy for directly calculating 10 x 50, either just adding a zero or building from 10 x 5 (which he would calculate as 10-20-30-40-50), or 50-100-150-200-250-300-350-400-450-500.
  • J1: well, I know 20 pounds is 1000 baht.  Then 10 is half of 20 and 500 is half of 1000.
  • D: Interesting.  How many 20s are in 100?
  • J1: (thinking) 5000 baht in 1000 pounds!
some conversation about what  you can buy with 5000 baht.
  • D: what about 15,000 baht.  How many 5,000s are in 15,000?
  • J1: 3, so 300 pounds.  Wow, that's a lot

Why did I find this so interesting?
First, I was really surprised by the strategy to calculate 10 x 50.  This reinforces the magical phrase "how did you think of that?" Sometimes my own preferred approach seems so obvious that I feel there won't be anything interesting gained by hearing the child's approach and, in this case, asking the question was just because I wanted to build a good habit.  I was so surprised by the answer that I forgot to tell him about an alternative strategy.

Second, there had been several other times earlier in the day when I tried to lead him into a mathematical conversation and he wasn't taking the bait. I guess I should relax and see where chances arise instead of controlling it.

Ok, but 1001 Arabian Nights?
We've started reading the Project Gutenberg version of 1001 nights. Nice mathematical title, no? Well, tonight we started The Story of the Husband and the Parrot. What you need to know is:

I am reading the story of Sheherezade to J1 and J2.  In this story . . .
. . . Sheherezade is telling King Shahriar The story of the Fisherman, in which . . .
. . .the fisherman is telling a genie The Story of the Greek King and the Physician Douban, in which . . .
. . .the King tells his Vizir about a story told by another vizir to King Sinbad, in which . . .
. . . we get The story of the Husband and the Parrot (which involves the Parrot telling the Husband a short story).

Counted generously, that's 6 stories-within-a-story.  And now I've told you, so that's 7 layers.

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