This is simple, but I'm missing the last step. I've almost got the answer. --The standard kilogram is a platinum-iridium cylinder 39.0 mm in height and 39.0 mm in diameter. What is the density of the material? I know that the correct answer is 2.15 x 10^4 kg/m^3. If someone could tell me how to get from my answer, 2.15 x 10^-5, TO 2.15 x 10^4 I would really appreciate it. Thanks.