Assume the density of air was measured as 1.00 kg/m3 ± 5%. The room has dimensions 4 m × 5 m × 2 m, each measured with 10% relative error. What is the mass of the air in the room? What is the relative error for the mass? I think this is a very simple problem, and i found what the mass of the air would be, i just don't understand relative errors, so how do i find the relative error for the mass? D = m/V D = 1.00 kg/m3 V = (4 m *5 m *2 m) = 40 m3 m = (1.00 kg/m3)/ (40 m3) m = .025 kg → m = .03 kg relative error: Is it something like 5%/ 10% ??