Question

the total surface area of a solid right circular cylinder is 231cm2 it's curved surface area is 2/3of total surface determined the radius of its base and height

Answer 1

the total surface area of cylinder =231cm2

=> 2πr(r+h)=231 cm2

=> 2πr2+2πrh=231 cm2--------(a)

its curved surface area is=2/3(231)cm2(given)

=> 2πrh=154 cm2 --------(b)

putting value of 2πrh from equ. (b) in equ. (a) we get

=> 2πr2+154=231

=>2πr2=231-154

=>2πr2=77

=>r2=77/(2π)

=> r2=12.25   (since π=22/7)

=> r=(12.25)1/2 cm = 3.5 cm

to find the value of h

now by putting the value of r=3.5cm in equ. (b) we get

=> 2πrh=154

=> 2(22/7)*3.5* h=154

=> 22h=154

=> h=154/22 cm = 7cm

Answer 2

yes answer is 7 çorrect