L x W x H is what you use to find the volume of a parallelopiped ...
like a cube or a box.
Cylinders and spheres don't have lengths or widths, and spheres
don't have heights either. The formulas for their volumes look different.
Cylinders and spheres both have a 'radius' ... that's the distance from
the center of a circle out to the curved edge of the circle. In a cylinder,
the circle is what you see when you look at one end of it. For the sphere,
it's just the distance from the center of the sphere to the surface, because
no matter what direction you cut the sphere, if your cut goes through the
center, then you always get the same circle.
Both formulas also involve the number called 'pi' (PIE). It's the number
that always pops up whenever anybody is doing anything with circles
and a lot of other things in math and science. The thing about 'pi' is
that it's impossible to write its exact value with digits ... the decimal
part of it keeps going and going and never ends. The beginning
of 'pi' is 3.14159 26535 89792 ... and it just keeps going forever.
In school, most teachers tell you to use 3.14 for pi. The answers
you get aren't exactly correct, but that's not a big deal, because the
answer is never the important part of the problem in school. The
important part is that you LEARN HOW to solve the problem and
find the answer.
In math and science writing, when pi has to be written down, it's
usually not written with digits at all. It's usually written with the
letter from the Greek alphabet called pi. It looks like this: π
Now, here are the formulas you asked for, for the volumes of cylinders
and spheres:
For a cylinder: V = π R² H
Volume = (pi) x (square of the radius) x (height of the cylinder)
square of the radius means ( R x R )
For a sphere: V = (4/3) π R³
Volume = (4/3) x (π) x (cube of the radius)
cube of the radius means ( R x R x R )
