Question

Find the radius of the base of a right circular cylinder whose CSA is 2/3 of the sum of the surface areas if two circular faces. The height of the cylinder is given to be 15 Cm

Answer 1

CSA of cylinder = 2 (pie) * r * h

Sum of Surface Area of two circular faces of cylinder
= (pie) * r2+ (pie) * r2
= 2 (pie) * r2

A/q
2 (pie) * r * h= 2/3 * 2 (pie) * r2
or r * 15= 2/3 r2  (eliminating 2 (pie) on both sides and putting the value of h = 15 cm)
or 2 r2 = 45 r 
or 2 r2 - 45 r = 0
or   r (2 r - 45) = 0
or (2 r - 45) = 0 (since 4 cannot be 0)
or r = 45/2 = 22.5

Answer 2

Answer:

2 (pie) * r * h= 2/3 * 2 (pie) * r2

or r * 15= 2/3 r2  

or 2 r2 = 45 r  

or 2 r2 - 45 r = 0

or   r (2 r - 45) = 0

or (2 r - 45) = 0

or r = 45/2 = 22.5

Step-by-step explanation: