Root mean square velocity of CO2 molecules

[Plasma]

1. The problem statement, all variables and given/known data

If the translationa speed of the water vapor molecules (H2O) in ir is 648 m/s, what is the translational rms speed of the carbon dioxide molecules in the same air? Both gases are at the same tmperature.

2. Relevant equations

V^2 = (3kT)/m

3. The attempt at a solution

I'm not even sure where to begin. I don't understand how knowing the water's speed helps me find the CO2's.

[Astronuc]

A good reference.
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/kintem.html#c2

But knowing that V^2 = (3kT)/m and that the H2O and CO2 have the same temperature T, what can one say about V2/m for each molecule?

[Plasma]

They must be the same.