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###### make r the subject of v=4/3 pie r^3

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12 years ago

make r the subject of v=4/3 pie r^3 need some help guys

Original post by Thrug

Simply rearrange to get r = ....

How do i do it

Reply 3

12 years ago

Divide both sides by Pie, then multiply both sides by 3/4. finally cube root.

Original post by james.h

What are you stuck on?

Rearrange to get all terms in r (i.e: the r^3 term, in this case) on one side, and everything else on the other side.

Given $r^3 = \cdots$, then taking the cube root of both sides will give you an expression for r.

Rearrange to get all terms in r (i.e: the r^3 term, in this case) on one side, and everything else on the other side.

Given $r^3 = \cdots$, then taking the cube root of both sides will give you an expression for r.

can you show me how

Original post by daviesblue

Divide both sides by Pie, then multiply both sides by 3/4. finally cube root.

dont you mean times both sides by 3

Original post by gorila7

can you show me how

I'll work through a different example to show you the ideas involved.

The volume of a cone is $V = \frac{1}{3} \pi r^2 h$

Multiply both sides by 3 to get rid of the 1/3: $3V = \pi r^2 h$

Divide both sides by pi: $\frac{3V}{\pi} = r^2 h$

Divide both sides by h: $\frac{3V}{\pi h} = r^2$

Take the square root of both sides: $\sqrt{\frac{3V}{\pi h}} = r$

Your example is very similar.

Original post by james.h

I'll work through a different example to show you the ideas involved.

The volume of a cone is $V = \frac{1}{3} \pi r^2 h$

Multiply both sides by 3 to get rid of the 1/3: $3V = \pi r^2 h$

Divide both sides by pi: $\frac{3V}{\pi} = r^2 h$

Divide both sides by h: $\frac{3V}{\pi h} = r^2$

Take the square root of both sides: $\sqrt{\frac{3V}{\pi h}} = r$

Your example is very similar.

The volume of a cone is $V = \frac{1}{3} \pi r^2 h$

Multiply both sides by 3 to get rid of the 1/3: $3V = \pi r^2 h$

Divide both sides by pi: $\frac{3V}{\pi} = r^2 h$

Divide both sides by h: $\frac{3V}{\pi h} = r^2$

Take the square root of both sides: $\sqrt{\frac{3V}{\pi h}} = r$

Your example is very similar.

is my answer the cubed root of 3v/4 pie

Original post by gorila7

is my answer the cubed root of 3v/4 pie

$r = \sqrt[3]{\frac{3V}{4\pi}}$

Original post by james.h

$r = \sqrt[3]{\frac{3V}{4\pi}}$

Thank you very much sir. I rep you

Original post by rykellim

There is an answer which shows "R= Cube Root of (6V/PI) / 2" in an assessment book. Does anyone know how the author went to this final answer instead of what was given by James H. above?

Any idea?

Any idea?

3V/4 = 6V/8 so they've just taken the cube root of 8 (i.e. 2) outside the root sign

Reply 13

2 years ago

Show working pls

Original post by Grace Billy

Show working pls

Please don't resurrect 10 year old threads

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