# How to find partial pressures of gases only given their percentages?

How do I find partial pressures if I am only given their percentages? Where do I begin?

Example: Assume $\ce{O}=21\%$ , $\ce{N}=78\%$ , $\ce{Ar}=1\%$ by volume. How would I calculate the partial pressures if total pressure is $\pu{1 atm}$.