Given,

Total surface area of hollow cylinder = 4620 cm²

Area of base ring = 115.5 cm²

Height of cylinder = 7 cm

Let outer radius of hollow cylinder = R cm

Let inner radius be = r cm

= πR² –πr² = 115.5 ………. (i)

And,

2πrh +2πrh+ 2(πR² – πr²) = 4620 ……………….(ii)

(putting value of (πR² – πr²) from (i) to (ii) )

=2πh(R+r) = 4620 -231 = 4389

= π(R+r) =………………..(iii)

From equation (i)

=π(R² – r²) = 115.5

= π[(R+r)(R-r)] = 115.5

(putting value of π(R+r) from equation (iii))

=