How fast does the propane molecule travel?

Question

can someone explain to me how to do this problem step by step??

Methan CH4 and propane C3H8 are 2 components of the natural gas burned in Bunsen burners. If a methane molecule travels at 675 m/s from a gas jet, how fast does the propane molecule travel?

Answer 1

http://en.wikipedia.org/wiki/Graham%27s_...

i.e the more massive it is the slower it travels

rate 1 / rate 2 = (MW2 / MW1)^1/2

675 / rate 2 = [( 44.1 g/mol C3H8)/ (16.04 g/mol CH4)]^1/2

675 / rate 2 = [2.75]1/2

675 / rate 2 = 1.66

rate = 675 / 1.66

your answer is 407m/s