Let’s see: 26 + 17 + ??
6 and 6 are 12. Plus one is 13.
2 and 1 are 3. Plus the carried one from the 13 make 4.
The answer is 43. Took about 5 seconds to do in my head, even without being able to add 6 and 7 directly.
I’m not sure how, exactly, that “common core” method is supposed to come up with an answer.
26 and 10 is 36, and 7 is 43.
I think you’re supposed to do it like this:
26 + 17 = (30 - 4) + (20 -3)
26 + 17 = (30 + 20) + (-4 -3)
26 + 17 = 50 -7
26 + 17 = 43
Is this simpler, clearer, offer more insight or require fewer manipulations than:
26 + 17 = (20 + 6) + (10 +7)
26 + 17 = (20 + 10) + (6 +7)
26 + 17 = 30 +17
26 + 17 = 43 ?
I’ll keep and open mind. I am sure it will actually end up confusing more gammer skool math teachers than it will enlighten any students.