The Math Princess

I often talk about the Unknown Son. All in all, it's not surprising given his struggles with cancer. But today I'm going to brag about the Unknown Daughter for a bit.

She gets $4 in allowance per week. Since we started giving the kids allowances, they've had piggy banks that are divided in three parts - the Church, the Bank, and the Store. They have to put 10% of their allowance in the Church, and this is put in the plate at Sunday School. The remainder goes half in the Bank (their long-term savings) and half in the Store (the amount they can s0pend). Any additional money they earn or get can be spent as they please.

They already know that 10% of a number is just throwing away the last digit. So, the other day, Unknown Daughter (7 years old and in first grade, BTW) asked how much $3.60 (the amount remaining after she takes 10% out of her $4.000) was when split in two. I asked her how much SHE thought it was. She went into the other room, and came out a few minutes later, saying $1.80. I asked her how she got this number, and this was her answer:
  • I couldn't split $3 into two, but I can split $2 into 2 $1's . So this left me $1.60.
  • I Don't know how to split $1.60, but that's just $1 and $0.60.
  • So, I split the $1 into 2 $0.50's and the %0.60 into 2 $0.30's
  • Then I added up the pieces - $1 + $0.50 + $0.30
I thought that was pretty sophisticated reasoning for a first grader (heck - even for a third grader) - and she did it without paper and pencil, too. So, I asked her how much $12.80 was if you split it into 2 pieces. Then I asked her how much $6.40 was split into 2, - this gave us 4 pieces of $3.20. Then we split it into 8 pieces of $1.60, and so on. Finally, we put the whole thing into a table - 1 $12.40, 2 $6. 40's 4 $3.20's, and so on all the way to and so on down to 256 0.05's. And yes, SHE did all the calculations.

She then noticed that the left hand column (the number of pieces) twice as big each time going down the column and the right hand side (the $$ value of each piece) got twice as big going UP the column. We did a few more examples at HER request (she thought the whole thing was a blast).

Finally, she went into her room and came out a few minutes later with a drawing of a girl with a crown on her head, titled "Unknown Daughter - The Math Princess".

Not bad for a first grader, eh? Of course, I'm totally unbiased.

Update (1/4/08): Unknown daughter came to me today and said "Daddy - I decided I don't want to be called the Math Princess. From now on, I want to be called the MATH RULER." That's my girl.