1. The problem statement, all variables and given/known data not really a question, just stuck with something. An airflow of 300 CFM has a contains 0.0387% CO2 (carbon dioxide-naturally occurring in air) flows through two ends of an rectangular open container from an exhaust fan located at the bottom. Within the container 100% CO2 can be added through a controllable valve. This air will mix instantly with the passing .0387 300CFM airflow. How much CFM of the 100%CO2 is required to add to the airflow to create a mixture of gases that = 0.5% CO2 2. Relevant equations 3. The attempt at a solution I tried setting up a simple addition formula: [(300CFM)/(.0387% CO2)] + [(x)/(100% CO2)] = (300+XCFM)/? I'm not sure if this is even close to being right, even if it is...i don't remember how to find the new percentage of CO2 after adding a certain volume. Maybe if the air was constant it would be easier for me...i just can't get my head around the whole "flowing" concept.