Generally, I allow as much time as they need to do this because it is an
opportunity for students to practice an essential feature of inquiry: developing
a procedure to solve a problem. It is likely that students will have some difficulty coming up with a procedure. Inevitably, some
groups will try to only use the ruler to measure the
thickness only to find out that it cannot be done. If
the class has made several unsuccessful attempts to
solve the problem, I write on the board: (1) density
= mass/volume; (2) mass is measured in grams; (3) volume
is measure in milliliters or cm3; (4) the volume
of a solid can be measured by how much water it displaces;
and (5) a centimeter cubed is the same as a cubic
centimeter (cc).