Rearranging this power equation

[JohnLIreland]

This particular area of my maths is way rusty. The formula I'm using calculates the metres of paper available (Y) from the thickness of a roll of paper (X) is:

Y = Factor *(Pi*(X+48.5)^2-7390)

I 'm trying to rearrange the equation to get X as the calculated value with Y as the variable. The roll has a cardboard tube in the centre and I want to calculate the thickness of the paper on the roll when wound with a given length of paper.

I've balanced it to

(Y/Factor+7390)/Pi = (X+48.5)^2

but I'm having a devil of a job pulling X out on its own.

Anybody help?

[tell-me-more]

I don't know how you got to the formula in the first place but the formula for X would be:

[(Y/F +7390)/Pi]^1/2 -48.5

I'm only writing it like that because I can't find a square root symbol, but x is the square root of the left hand side of your equation, minus 48.5.

Hope that helps!

[JohnLIreland]

Thanks tell-me-more. Your answer wasn't quite right but it did put me in the right direction. Using your formula with a bit of trial and error the formulation that gave me the correct thickness from my known meterage was:

=SQRT[( Y / Factor+7390)/Pi] -48.5

(it didn't need raising to the 1/2)

FYI, the original equation came to me via my supplier.

Cheers!

[fo3nix]

I can confirm that your equation for X is correct.

[vascop]

tell me more 's equation was TOTALLY correct. Raising to the power 1/2 is the same as taking the square root!!!