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 = ?
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,
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