rearranging

**Chez_** · December 11th 2007, 06:30 AM

Hi, could anyone please help me with this formula;

V=1/3 pie r^2h i need to make r the subject i di v-1/3=pier^2h
v-1/3-pie=r^2h
v-1/2-pie-h=r^2 then divide by 2 but i dont think thats realy going to be right and i tried a few others but im gtin into a muddle thnx for any help x

**janvdl** · December 11th 2007, 06:39 AM

Originally Posted by Chez_

Hi, could anyone please help me with this formula;

V=1/3 pie r^2h i need to make r the subject i di v-1/3=pier^2h
v-1/3-pie=r^2h
v-1/2-pie-h=r^2 then divide by 2 but i dont think thats realy going to be right and i tried a few others but im gtin into a muddle thnx for any help x

$V = \frac{1}{3} \pi r^2 h$

$3 V = \pi r^2 h$

$\frac{3 V}{\pi h} = r^2$

$r = \sqrt{ \frac{3 V}{\pi h} }$

**kalagota** · December 11th 2007, 06:42 AM

Originally Posted by Chez_

Hi, could anyone please help me with this formula;

V=1/3 pie r^2h i need to make r the subject i di v-1/3=pier^2h
v-1/3-pie=r^2h
v-1/2-pie-h=r^2 then divide by 2 but i dont think thats realy going to be right and i tried a few others but im gtin into a muddle thnx for any help x

awww.. first of all, it is PI and not pie..

so, i recognize it as the formula of the volume of a cone.

$V = \frac{1}{3} \pi r^2h$ and you want to solve for r in terms of the others, is that it?

so, multiply 3 to both sides, then you will have $3V = 3\cdot \frac{1}{3}\pi r^2 h = \pi r^2 h$ .. multiply $\frac{1}{\pi h}$ , so that $r^2$ remains of the right side.. that is $\frac{3V}{\pi h} = r^2$ .. lastly, take the squareroot of both side, this will become, $\sqrt{\frac{3V}{\pi h}} = r$ .. then you are done..

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