Carlos 149 + 286 Written on paper Henry 149 + 286 Henry says, "I know that 40 and 80 is 120, and one hundred and two hundred makes 300, and 120 and 300 is 420, and 9 and 6 is 14, so 420 and 10 is 430, and 4 more is 434." Elliott 149 + 286   Written on paper Sarah 149 + 286 Sarah says, "Well, 149 is only 1 away from 150, so 150 and 200 is 350, and 80 more is 430, and 6 more is 436. Then I have to subtract the 1, so it is 435."

Maria
Manipulatives
 = 100 Called a flat = 10 Called a long = 1 Called a single

Maria uses manipulatives (base-ten blocks) to solve the problem. Maria says, "I took one flat for the 100 in 149 and 2 flats for the 200 in 286.

I took 12 longs: 4 for the 40 in 149 and 8 for the 80 in 286.

I took 15 singles for the 9 in 149 and the 6 in 286.

Then I counted like this, '100, 200, 300'; then for the longs, '310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420'; then the singles, '421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435.'

3.2. If you were a teacher, which of the approaches would you like to see children share? Select "Yes" or "No" next to each student's name, and then explain your choice.

 Carlos Yes No Henry Yes No Elliott Yes No Sarah Yes No Maria Yes No

3.3 Consider just the strategies on which you would focus in a unit on multidigit addition.  Over a several-weeks' unit, in which order would you focus on these strategies?

 First: no preference Carlos Henry Elliott Sarah Maria I don't want to share any others Second: no preference Carlos Henry Elliott Sarah Maria I don't want to share any others Third: no preference Carlos Henry Elliott Sarah Maria I don't want to share any others Fourth: no preference Carlos Henry Elliott Sarah Maria I don't want to share any others Fifth: no preference Carlos Henry Elliott Sarah Maria I don't want to share any others

 3.4.  Do you think that Carlos could make sense of and explain Sarah's strategy?  Why or why not? 3.5. Do you think that Carlos could make sense of and explain Elliott's strategy?  Why or why not?