Question

a 20 cm nail just fits inside a cylindrical can. three identical spherical balls need to fit entirely within the can. what is the maximum radius of each ball?

1. thuthuy
The maximum radius of each ball is 3.33 cm.

### What is a Cylinder?

A cylinder is a three-dimensional figure which is made of two parallel circular bases separated at a certain distance by a curved surface of the same radius as that of the bases.
A 20 cm nail perfectly fits the cylinder.
So the height of the cylinder = 20cm.
A sphere is a three-dimensional geometrical figure analogous to a circle. All the points of the sphere are at the same distance from the center.
If 3 spheres have to be fitted inside the cylinder,
The sum of the diameter of the spheres will be equal to the height of the cylinder.
The spherical balls are identical and so will have the same diameter
Let the maximum diameter of the sphere that can fit in the cylinder is d cm
Then,
d + d + d = 20
3d = 20
d = 20/3 = 6.67 cm
r = 3.33 cm
The maximum radius that the spheres can have to fit in the cylinder is 3.33 cm.