19. solve for r: c=2pi r
a) r=c/2pi
b) r=2cpi
c) r=2pi/c
d) r=1/2cpi

The correct answer is:  [A]:  " {r = C /  2 pi} " .

Explanation:

Given:

  " C = 2 * pi * r "  ;  isolate "r" on one side of the equation ; 

Divide EACH SIDE of the equation by:  "2 * pi " ;

C / (2 * pi)  = (2 * pi * r) / (2 * pi) ;

C / (2 * pi) = r ; 

↔  r = C / (2 * pi) ;  which is:  Answer choice:  [A]:  " {r = C /  2 pi} " .

I’ll you if you answer my questions!