Have a jar filled with beans, buttons, etc. at each table when students arrive. Also have mini-cups available at the tables. Have the students individually guess how many items are in the jar and write down how they came to that conclusion. Let them know that they may do what they like with the contents of the jar with the exception of counting the pieces individually. It is interesting to see which students use the mini-cups to take a sample count to estimate the total amount of pieces in the jar. Discuss different methods of computation. And then have them find the actual counts to compare to their estimations.