How do i predict the rate of effusion?

Question

If a sample of CH4 effuses at a rate of 9.0 moles per hour at 35 degrees celsius, which of the gases below will effuse at approximately twice rate under the same conditions?

a. CO
b. He
c. O2
d. F2
e. SiH4

Please show your work... Thank You!

Answer 1

Root of 16 is 4. Now halve that, to get 2, and square it to get four.
So it's He. Look up Graham's Law.