Density of Rocks Part A Nguyen uses a triple beam balance to measure the mass of each rock. Read the values on the balance for rocks X, Y, and Z. Rock Balance Reading of Rock Mass (g) X triple beam part of mass balance with top beam with pointer at 20, middle beam with pointer at 0, and lowest beam with pointer at 1 Y triple beam part of mass balance with top beam with pointer at 10, middle beam with pointer at 0, and lowest beam with pointer at 7 Z triple beam part of mass balance with top beam with pointer at 20, middle beam with pointer at 0, and lowest beam with pointer at 6