Rearrange A = 2 x pi x r x h?
I've got this maths question:
The formula for the curved surface area, A, of a cylinder is A= 2 x pi x r x h
where r is the radius and h the height.
How would you rearrange this formula so that r is the subject?
Thank you! 
Comments
To rearrange this formula to make r the subject we have to perform the inverse operations on our values. In other words we have to do the opposite thing to them and move them around to where we want them.
Hopefully you can see this in what i do. First we write it out and figure out what we need to do. To get r on its own we need to move 2Pi and h to the other side of the equals sign. To do this we perform inverse operations on both sides of the equals sign.
A = 2 * Pi * r * h
A / (2 * Pi * h) = (2 * Pi * r * h) / (2 * Pi * h) -------- Here i perform the operation on both sides.
A / (2 * Pi * h) = r --------- r is the only thing left on this side after the operation
r = A / (2 * Pi * h) --------- Re-writing it so r is at the front
There is our answer.
A = 2 x pi x r x h, to solve for r just simply divide both sides by 2 x pi x h
A/(2 x pi x h)= r, answer
A / 2 x pi x h = r
In algebra we don't need an x to indicate times.
A = 2 pi r h
to rearrange and find r.
well this is easy, there's just one r on the right hand side, so if we just divide by eveything that isn't r we will have r.
A/(2 pi h) = r
It's that simple.
You have to get r on its own! First remember that the multiplication can be done in any order so this can be written A=(2xpixh) x r
Then separate the bracket by dividing by the whole bracket, as a bracket can be treated as a single term.
Then you get A/ (2 x pi x h) =r
r = A / ( 2 h pi)
r = A/(2*pi*h)
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A = 2πrh
r = A / 2πh
2ÏRH = A
Divide the 2, the Ï and the H from both sides, leaving:
..........A
R= ------------
........2ÏH
Dan