Wednesday, October 28, 2015
This problem is from Engageny math. Here's the sheet I assume it appeared on. Grade 2 - Module 3.
Here's Andrew Gelman.
Speaking as a writer, and as a parent who spent a lot of time teaching my son and myself grade-school math, I don't like the wording at all.
"Sally did some counting" ---- the word "count" means count by ones, especially to a 2nd grade child.
Plus the question about why Sally did what she did invites commentary on Sally, not Sally's method.
Is there a way to ask this question that makes more sense?
And is there a reason to ask it this way -- to ask a student to analyze Sally's answer -- rather than to ask the student to use 1s and 10s to count up to 214?
I have to say .... offhand, I see no reason to ask this question this way.
I would much rather see this as a story problem about giving change.
Sally has pennies and dimes in her pocket.
Her friend Jane sells her a glass of lemonade for $2.14.
Sally gives her $1.77.
How many more pennies and dimes does Sally owe?
That wording doesn't produce the specific sequence, of course ....
What if you just said, "Count up from 177 to 214 using the fewest (whole) numbers you can. You can count by 1s or skip-count by 10s."
Here's a question.
Does "skip counting" by 10s only mean 10, 20, 30, etc.?
Can it mean 177, 187, 197?