Jack knows the surface area of a cylinder and its radius. he wants to find the cylinder's height. he needs to rewrite the formula a=2πr (r+h) to find the cylinder's height (h) in terms of the cylinder’s surface area (a) and its radius (r). which is the correct formula?
a. h= r+ a/2πr
b. h= a/2πr
c. h= a/2πr-r^2
d. h= a/2πr-r

answer: can and shows the work

step-by-step explanation:

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional