Question

A Water tank is 528cm long and 42cm wide. it containswater to a depth of
18cm. four identical spheres are placed in the tank and are fully
submerged .if the ater level rises by 7 cm, calculate radious of
spheres?

Answer 1

The tank is in the form of cylinder
its radius is 24 cm and it height till 
volume of water intially
$V= \pi r^2h=1357.168 cm^3$
now four sphere of radius r' are added
so the final height is 18+7=25cm
Volume of water Finally
$V'= \pi r^2h= \pi (24)^2(25)=1884.96 cm^3$
So the difference between the final and intial values will give the volume of spheres
$4V_{sphere}=V'-V=527.79 cm^3$
$V_{sphere}=131.95 cm^3$
$\frac{4}{3} \pi r^3_{sphere}=131.95$
$r_{sphere}=5.612486 cm$