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.
There are 609.6 centimeters in 20 feet
20 yards is 60 feet.