First, we need to find the volume of the aeroplane and the tennis ball.
Once we get these figures, we will divide the volume of the airplane with that of the tennis ball.
The formula for the cylinder is = πr2h
Estimating that an airplane has an approximate radius of 1 meter (assuming the aeroplane has the same height of a normal office floor) and length 33 meters (400 seats in an aeroplane with 10 seats a row which gives us 40 rows and adding another 10 rows for pilot and toilets we get to 50 rows * 2 feet which gives us 100 feet or 33 meters).
The volume of aeroplane is 103m^3 or 33πm^3 or 33mπcm^3
Then, estimating that tennis ball has a radius 3.3cm we can calculate the volume.
In that case, the volume of the tennis ball can be calculated by the formula of a sphere.
Volume of a sphere is = (4 πr3)/3
The volume of the tennis ball would be 47.916πcm^3.
Finally, after dividing the volume of the aeroplane by that to the tennis ball we arrive at 688,705.
Therefore, we can fit approximately 688,705 tennis balls in a Boeing 747.