Question

S = 2πrh + 2πr², for h

A. h = S/2πr -1
B. h = 2π(S - r)
C. h = S - 2πr²/2πr
D. h = S - r

Answer 1

Explanation:

This is a literal equation, and for some reason, students literally freak out about solving them. We will isolate h the same way we would if we were solving an equation for x. In order to get the term with the h in it all by itself, we have to move everything else away from that term. The 2πr² is added on the left, so we will move it by subtracting it from both sides, giving us

`S-2\pi r^2=2\pi rh`

Then we need to get the h alone. Everything on the right side of the equals sign is multiplied together, so the "undoing" of multiplication is division, so that's what we'll do. Divide everything away from the h:

`(S-2\pi r^2)/(2\pi r)=h`

which is choice C.