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## Comment on

Volume of Sphere## Why can't we use volume of

## That's totally acceptable,

That's totally acceptable, except most people don't know that formula, and the formula is not required knowledge for the GRE.

So, the solution provided in the video shows that we can solve the question by applying logic rather than by using a formula.

## Is sphere included for gre

## As I mention at the beginning

As I mention at the beginning of the video, you do not need to know the formula for the volume of a sphere. However, you should know what a sphere is, since it's possible that there could be a question involving a sphere.

## wooow. mathematical magic

## Clever approach. I think I

## Ha!!! I love it!

Ha!!! I love it!

## Last thing. After seeing

Volume of sphere = 1/2 • volume of cube • 1.05

V = 1/2 • diameter^3 • 1.05

or

Volume of sphere = .53 • volume of cube

V = .53D^3

I don't know if anyone else would find this particularly useful, but I thought it was interesting.

## Interesting indeed. It

Interesting indeed. It certainly LOOKS like such a sphere would fill up way more than half of the cube. My calculations say that a sphere takes up 52.3% of the cube's volume.

## I had one more question about

Regarding my previous comment on spheres, you are right it is 52.3. Since then I've thought that (π/6)D^3 is a good way to remember volume of a sphere, because you can see in the expression that the volume of a sphere approximately half of the volume of a corresponding cube, and it keeps the π in the calculations.

## That would seem like a good

That would seem like a good way to calculate the volume of a sphere. The problem with that approach is that, if we slice a sphere into tiny circles, the size of the circles vary.

On the other hand, if we slice a CYLINDER into tiny circles, the size of the circles are always the same.

Cheers,

Brent

## Will NEVER be on the ***king

## I agree that you don't need

I agree that you don't need to know the volume of a sphere. In fact, that's the very first thing I say and my solution.

The one logical step required solve this question is well within the scope of the GRE, especially when you consider the fact that Quantity B is three times the value of Quantity A.