1. The problem statement, all variables and given/known data An amonia NH3 molecule in the figure has three hydrogen atoms, which form a equilateral triangle as the base of a pyramid. At the top of the pyramid is the nitrogen atom. The length between any two hydrogen atoms is 9.4x10^-11, the length from nitrogen to any of the hydrogen atoms is 10.14x10^-11. The mass ratio of nitrogen to hydrogen is 13.9. The xaxis runs through the bottom of the pyramid, one of the points lies on it. The y axis runs through the center of the pyramid vertically. 2. Relevant equations 3. The attempt at a solution I am getting a close answer, but off enough to think I'm doing something wrong. x center of mass is 0, by symmetry/intuition. For y, what i did was try to find how high nitrogen is with the pythagorean theorem. I got that nitrogen should be at a height of 3.8x10^-11 along y axis. I multiplied this number by 13.9, then divided by 16.9. My result is 3.125x10^-11 for the ycom, but the correct answer is 3.08x10^-11. Why am I off by that amount?