Here we need to find the volume of each spherical ball using the given values of the diameter and then we combine those values and find the diameter .
For the first ball, diameter is 2 inches, so radius =1 inches
For the second ball, diameter is 4 inches, so radius = 2 inches
For the third ball, diameter is 6 inches, so radius =3 inches.
Now we use the given formula of the volume of sphere.
[tex] V_{1} = \frac{4}{3} \pi (1)^3, V_{2} = \frac{4}{3} \pi (2)^3,V_{3} = \frac{4}{3} \pi (3)^3 [/tex]
[tex] V_{1} = 4.2 , V_{2} =16.755, V_{3}= 37.7 [/tex]
Total volume = 4.2 +16.755 + 37.7 =58.655
Now we have the volume and using the given formula of volume of spher, we can find out the radius .
[tex] 58.655= \frac{4}{3} \pi r^3 [/tex]
[tex] r = 2.4 [/tex]
So diameter = 2 * 2.4 = 4.8 inches