Saw a neat post from Michael Pershan last night:
One of the reasons it caught my attention was that my younger son has had to change the way he does subtraction. Sadly the reason for the change is that the standardized testing up here tests borrowing and carrying. Ugh.
Anyway, I thought it would be interesting to hear him work through this problem since subtraction is back to being new to him. Here’s what he did (as well as his explanation of borrowing and carrying):
Next we scrolled through Pershan’s blog post. I wanted to see how my son would react to the different solutions. The solution that used addition rather than subtraction was the one I was particularly interested in him seeing:
So, an interesting exercise – especially viewing and trying to understand the other solutions.
Mike's Math Page 