I used this task with my 3rd grade students. Students had been previously introduced to rounding numbers. This task was part of the introduction to estimation. In order to make a claim, students had to first round the numbers, and then add the rounded numbers to find the estimate. The task required students to state a claim and argument, as well as include what their partner said.

Microsoft Word version: 3_OA_EstimationAddition_Problem_Construct

PDF version: 3_OA_EstimationAddition_Problem_Construct