1. The problem statement, all variables and given/known data A penny has a mass of 2.5 g and is 1.5 mm thick; a nickel has a mass of 5.7 g and is 1.9 mm thick. If you make a stack of coins on a table, starting with five nickels and finishing with four pennies, how far above the tabletop is the center of gravity of the stack? 2. Relevant equations Y center of gravity = (y1m1+y2m2+y3m3 etc) / (m1+m2+m3 etc) 3. The attempt at a solution Ycg = (5*(5.7*1.9)+4*(2.5*1.5)) / ((5*5.7) +(4*2.5)) Ycg = 1.80 mm This answer doesn't make sense because the entire stack is roughly 15 mm high... What am I doing wrong?