Math Is Fun Forum

Rainer

Guest

round bottem tube

Hi there,

to caculate the volume of a testtube is not so difficult.

how do I change the formula when only volume and diameter ore hight is given?

V = π*r²*h+(((π*d³)/6)/2)

h = ?

d = ?

Regards,
Rainer

Bob

Administrator

Registered: 2010-06-20

Posts: 10,643

Re: round bottem tube

hi Rainer

Welcome to the forum.

To make h the subject when d and V are known is fairly straight forward:

Getting d as the subject when V and h are known will not be so straight forward, because the 'd' term will occur as a square and a cube.

There are algebraic ways to solve a cubic, but it's not going to be easy to come up with a 'nice' formula.  If you have specific values to substitute in, it's probably easiest to use this format and then try to solve for d from there.  There are numerical methods that will get d that are easier to use.

Hope that helps, 

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob