Expert: Pawan Musale - 9/14/2009

Question
I'm trying to understand how to solve this problem.
Volume of sphere

Volume=4/3 pie r^3
If given a problem I cannot do it because I don't know what to do with the 4/3.

How do I break it down or multiply it on both sides..I'm so clueless.

Answer
Hi Olivia,

Volume (V) of sphere is given by formula,

V = 4/3 pie r^3

which is

V = (4/3) * pi * radius^3 -------------------------- #1

So whenever you have been given a problem, you have to multiply pi with cube of radius and then multiply the result with 4/3.

Let us take one example:

Calcualte volume of sphere whose radius is 3 cm.

Now, we have r = 3

Putting this value in equation #1 above,

V = (4/3) * pi * 3^3
V = (4/3) * (22/7) * 3 * 3 * 3   ... (pi = 22/7)

3 is in denominator in 4/3, and radius 3 is in numerator.
Hence cancelling these two terms,

V = 4 * (22/7) * 3 * 3
V = 36 * (22/7)
V = 113.14 cubic cm

So to summarise, (4/3) is a constant term which will multiply with rest of the expression.

I hope this clarifies your concern.

All the best.

Regards,
Pawan