A mercury barometer reads 740 mm on the roof of a building and 760.0 mm on the ground. Assuming a constant value of 1.29 kg/m3 for the density of air, determine the height of the building. Okay I understand to find the h I use the formula h=patm/densityxg, and P2-Patm=pgh yet I am confused amd I supposed to convert the 740 and 760 to atm? When I do this calculation I get .02 differnce subtraction Patm from P2. Do I first have to find the density of the mercury and then compare it, or do I use it within the same formula that I use to find the height of the building. The order and addition of the steps confuse me although I thinkI have al the right formulas to find everything.