Some endurance athletes (such as cyclists and long distance runners) use a hypobaric cha...

Some endurance athletes (such as cyclists and long distance runners) use a hypobaric chamber to enhance their ability to use oxygen. A hypobaric chamber mimics the effect of being at a high altitude, where the amount of oxygen available to the lungs is less than at sea level. A typical hypobaric chamber simulates the environment at an altitude of 9000 ft above sea level, where the air pressure is approximately What is the amount of oxygen available at this altitude compared with that at sea level? Express your answer as a fraction (without units).