This is a sample of student work from their math Journals. The students have been working with subtracting double digit numbers. When looking through this students work I noticed that she got the first 2 problems correct and the next 3 wrong, and did not even answer the last question. When asked to make ballpark estimates for problem 3 and 4 she chose numbers that were closest to those numbers and got those right. However, when she did the actual math she was off by a few numbers. Some of the things I am really curious about is 1. Why did she choose to ballpark to those numbers? 2. How does the teacher want them to ballpark numbers. Also I was not present at the time when the teacher explained what problems to do but 3. Did this student completely avoid problem 6 or was she given specific directions not to solve the problem. If so, I would be curious to see her answer the problem or at least attempt to solve a subtraction problem with a place in the hundredths. I think it would be fairly easy for me to answer these questions, if I had more time this day I would have been able to ask the teacher along with this particular student her thought process on her ballpark estimates and the last problem. One of the reasons I think this student chose to ballpark her numbers to these is because they are the closest numbers to the nearest tenth. I think using 50 for 47, and using 19 for 20 is something I and most students would probably do. So I think I can understand her thinking and it makes the most sense for the numbers she was given. However, I am curious as to how the student got the answer 25 when she subtracted 19 from 47 and how she got 55 when she subtracted 23 from 88. I can clearly see the student's thought process because she carries and borrows and shows her work on the paper. It is possible that this student was in a hurry and miscalculated. Since I think the big idea for this assignment was for the kids to be able to subtract double digit numbers, I think it would be best to further this students thinking with more double digit subtraction and not having her give ballpark estimates first. I think that might have confused her and maybe in the process caused her to get her numbers mixed up. I think it would be important to encourage this student to write her problems out like problem 1 and 2 so she could clearly see the division between the two place values.