# One-third of an air tank is removed with each stroke of a vacuum pump. What part of the original amount of air remains after 5 strikes?

Part remaining after n strikes $= {\left(1 - \frac{1}{3}\right)}^{n}$
Part remaining after 5 strikes $= {\left(1 - \frac{1}{3}\right)}^{5} = \frac{32}{243}$
~~13.17% remaining