none,
atmosphere is a gas
the atmosphere is up to 100km after that you are in space.
20
20 x 20 = 400 square feet.
1 atmosphere is 33.9 feet of water.
Exactly 20 feet.
400
33.6 feet
Approx 33.8 feet.
400 square feet.
20 cm = 0.656 feet.
Do you mean a real square with the side length of 20 feet? Then 20 feet times 20 feet is 400 square feet.
60*20 = 1200 Sq feet
There are 609.6 centimeters in 20 feet