physics
posted by Jim .
On a perfect fall day, you are hovering at low altitude in a hotair balloon, accelerated neither upward nor downward. The total weight of the balloon, including its load and the hot air in it, is 24000 N.
Find the weight of the displaced air.
Find the volume of the displaced air.

The displaced air weight is 24,000 N.
Divide by the WEIGHT density of air to get the air volume.
http://en.wikipedia.org/wiki/Density_of_air 
20000