1. The problem statement, all variables and given/known data In the ammonia (NH3) molecule, the three hydrogen (H) atoms form an equilateral triangle; the center of the triangle is 9.40x10^(-11) m from each hydrogen atom. The nitrogen (N) atom is at the apex of a pyramid, with the three hydrogen atoms forming the base. The nitrogen-to-hydrogen atomic mass ratio is 13.9, and the nitrogen-to-hydrogen distance is 10.4x10^(-11) m. Locate the center of the molecule relative to the nitrogen atom. 2. Relevant equations Rcom=(1/M)(sum of MiRi from i=1 to n) 3. The attempt at a solution I have read through the problem several times, and I started to try and solve the problem by just figuring out the three-dimensional coordinates, but it seems a bit odd for the book to give such a tedious problem. Is there some sort of symmetry or way of re-drawing the problem to eliminate the z-axis that I am not picking up on, or do I really need to use all three axis to figure out the answer?