Polycarbonate plastic has a density of 1.2 g/cm3. A photo frame is constructed from two 3.0 mm sheets of polycarbonate. Each sheet measures 28 cm by 22 cm. What is the mass of the photo frame?

440 g First, determine the volume of each sheet. And it's easier if each dimension is using the same unit of measure. So each sheet is 28 cm by 22 cm by 0.30 cm. Multiply them together 28 cm * 22 cm * 0.30 cm = 184.8 cm^3 Since we have 2 identical sheets, double the total volume 184.8 cm^3 * 2 = 369.6 cm^3 Now multiple the volume by the density 369.6 cm^3 * 1.2 g/cm^3 = 443.52 g Round the results to 2 significant digits since all of the given figures are only 2 significant digits long. 443.52 g = 440 g