erm, ok lets say i have a value, with uncertainty, like y = 10 ± 3 so lets say i multiply y by 2, then it becomes 20 but does the uncertainty becomes 3 x 2 = 6? , hence y = 20±6 ? what about divide? does it becomes 1.5? i roughly understand fractional uncertainty and propagation of uncertainties, but what if i multiply the value of y with a constant as in the case above. what will become of the uncertainty? thanks for help!