New to my posts on estimating and counting routines? Check them out. They are quick and no prep lessons that get at a variety of important number skills and are easily differentiated to meet a variety of needs.
I completed this estimation and counting routine with a mixed group of second and third grade students. I wanted to work with numbers within 1000 so we used paper clips for our material. It is something I have plenty of.
|These are their initial estimates.|
|This is what the pile looks like after 600 have been taken out.|
|We looked at the other estimates in terms of how much bigger than 600 they were. Some kids realized they made their estimate to large.|
|The final count. Each of the 6 people has a pile of 100 and a pile of 30. There is one paperclip left in the middle of the table.|
Our final number was 781. Our time was up for the day. The following day we brought this number back to the whole group. I presented them with the context that I really wanted to have 1000 paper clips and needed their help deciding how many more I should order. Students had a few minutes to think to themselves and then shared their ideas with a partner. ALL of this was done mentally. Then they shared different strategies with the whole class. As they were sharing strategies, I wrote down equations that showed their thinking. I was truly impressed with the variety of strategies and mental math that was going on. Here is a peak at some of the ideas. This makes me feel like my work with problem strings and helping kids develop their own strategies for addition and subtraction is really paying off!
|These students added up from 781 to 1000.|
|These students subtracted from 1000. They started by subtracting 700 and then subtracted 80 and then 1.|
|This student used a fact they know about 100-78=22 to help them figure out 1000-780=220. Then they subtracted 1 more.|
|This student used skip counting to add 100 more twice then 10 more than 9 more. They added 219 in all.|
|These students tried adding 300 but got to much so they subtracted the extra 81. In their words, "if you add 300 and then take 81 back it is the same as adding 219."|
Have you tried estimating and counting routines in your classroom? How about problem strings?