Clarifications:

• What kind of soccer field are we seeing?

(professional artificial soccer field-fifa std, outdoor soccer field, indoor soccer field, mini football field??)

• Are we considering goal posts too?(yes)

• Shape of the goal net? Is it cubical/any other 3D shape

• What type of ball are we seeing? professional/indoor/turf/kids???

• Any dimensions in mind?

Assumptions:

• Type of field- professional soccer field.

• Dimensions: 90*45(m)-approx

• Goal post: dimensions: length=7m, breadth=3m, height= 3m

• Rectangular shape net, assuming no thickness for net

• Shape of goal net- cubical

• Shape of ball-spherical, professional soccer ball, dia=22cm

• On the soccer field without goal post, only 1 layer of ball are considered since area is considered not volume(assuming open field with nothing covered on top)

Calculation:

Area of soccer field without goalposts= 90*45 = 4050 m^2

Area of soccer ball = pi*r^2

          3.14*(0.11)^2

          0.038 m^2

Number of balls= area of soccer field/area of soccer ball (assumption balls are closely packed without any gaps)

Number of balls = 4050/0.038 = 106578 balls

Goals posts (balls)

Volume of goal post = l*b*h (cuboid)

7*3*3 = 63 m^3

Volume of ball= 4/3*pi*r^3 (sphere)

  4/3*3.14*(0.11)^3

  0.0056 m^3

Number of balls = vol of goal post/vol of ball

    63/0.0056 = 11250 balls

Since there are 2 goalposts = 2*11250 = 22500 balls

Total soccer balls that can be fitted into a soccer field = 106578 + 22500 balls

Final answer = 129078 balls