Question

Make r subject of the formula V=πr^2h. Make the stated variable the subject of the formula R in A= πRh+2πRh

Answer 1

1) Make r the subject of V = π r^2 h

V = π r^2 h
Divide by πh (assume h ≠ 0):
r^2 = V / (π h)
Take square root (physical radius nonnegative):
r = sqrt( V / (π h) )

(Algebraically r = ±sqrt(V/(π h)), but usually r ≥ 0.)

2) Make R the subject of A = π R h + 2 π R h

Combine like terms:
A = (π h + 2 π h) R = 3 π h R
Divide by 3πh (assume h ≠ 0):
R = A / (3 π h)