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."

Does Carlos's reasoning make sense to you?

Yes    No

Does Henry's reasoning make sense to you?

Yes    No

Does Elliott's reasoning make sense to you?

Yes    No

Would you like to see a further explanation?
Yes    No

 Click here  to see a further explanation.

Does Sarah's reasoning make sense to you?

Yes    No

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.' 

So the answer is 435."

Does Maria's reasoning make sense to you?

Yes    No