Get two volunteers. Give each volunteer 10-30 square childrens ABC blocks. (amount depends on what age you are working with, they will be stacking the blocks, so young children will not be able to stack as many) Tell the volunteers that they have an assignment to stack as many blocks as they can. One person will get approx. 10 seconds while the other gets 1 minute (again vary time according to age). Let the one minute person start first and then have the second person begin when there is 10 seconds left.