This one has been around for a while and I don't know where I saw it first. But thanks. And thanks to the #MTBoS
Students worked with a partner on this one. They were given a measuring tape and 10 beer cups and 10 styrofoam cups. Here is what I wrote on the board.
Others just found the number of cups and not the height.
The actual solution is on the bottom line.
Here is a photo of it: