Estimation vs. Calculation is one of many interactive math bulletin board ideas made available by Kutztown University.  Each of the bulletin boards is designed by a college student studying to become a teacher, has accompanying pictures, directions on how to replicate the board, and worksheets.  Most of them are for secondary school, but  I noticed a few, such as the Estimation one, that would be appropriate for upper elementary.  I especially liked the warning that appeared at the end of the instructions for Estimation vs. Calculation.  The creator, Sara Karahoca, states, “WARNING!!!!!! A bulletin board with candy is very enticing. NOT RECOMMENDED FOR USE WITH COLLEGE STUDENTS (as they will eat all your candy). NOT RECOMMENDED IN HIGH TRAFFIC/UNSUPERVISED AREAS (as students, hungry professional staff, and/or wild animals may also eat all your candy and steal your smiley faces.)”  A sense of humor always helps!