My first grade son was doing his homework this afternoon, and he was knocking out double-digit addition problems mentally and not even breaking a sweat. It was AMAZING to watch. I was so enthralled that I asked him to explain his process and I took dictation as he spoke:
“So I took the 40 and the 30 and I knew it was 70. Then I took the 7 and the 8 and I knew it was 15. Then I knew that 70 and 15 equaled 85.”
The “quick tens” were added after he calculated the answer.
“So I just took the 53 and 27 and added the 7 to the 3. I knew it equaled 60. I took the 2 and it was 20 and put it with the 60 and I knew it equaled 80.”
“Because I knew 8 and 8 made 16 and I knew 3 and 4 were 30 and 40 so that’s 70. So I added the 16 to the 70 and I knew it equaled 86.”
“So I knew 3 and 5 made 8 so I just took the 50 and 40 and knew it equaled 90. Then I took the 8 and the 90 and I knew it equaled 98.”
Props (and hugs) to his teacher!
The Real McCoy 