The total surface area of a hollow cylinder which is open from both sides is 4620 sq. cm, area of base ring is 115.5 sq. cm and height 7 cm. Find the thickness of the cylinder.

Explanation

Let the inner and outer radii of hollow cylinder be r cm and R cm respectively.
Then,
`2pih+2piRh+2piR^2−2pir^2=4620` …….(i)
and, `piR^2−pir^2=115.5` …….(ii)
`⇒2pih(r+R)+2(piR^2−pir^2)=4620 and, piR^2−pir^2=115.5`
`⇒2pih(r+R)+2×115.5=4620 and pi(R^2−r^2)=115.5`
`⇒2pi×7(r+R)=4389 and pi(R+r)(R−r)=115.5`
`⇒pi(R+r)=313.5 and pi(R+r)(R−r)=115.5`
`⇒(pi(R+r)(R+r))/pi(R−r)=313.5/115.5`
`⇒R−r=7/19cm`