The total surface area of a hollow cylinder which is open on both the sides is 4620 sq.

Let the inner radius of the hollow cylinder be r1 cm

The outer radius of the hollow cylinder be r2 cm

Then,

$2 \pi r_{1} * h+2 \pi r_{2} * h+2 \pi r_{2}^{2}-2 \pi r_{1}^{2}=4620 \ldots$ (a)

$\pi r_{1}^{2}-\pi r_{2}^{2}=115.5 \ldots$

Now solving eq (a)

$2 \pi r_{1} h+2 \pi r_{2} h+2 \pi r_{2}^{2}-2 \pi r_{1}^{2}=4620$

$\Rightarrow 2 \pi h\left(r_{1}+r_{2}\right)+2 \pi\left(r_{2}^{2}-r_{1}^{2}\right)$

$\Rightarrow 2 \pi h\left(r_{1}+r_{2}\right)+2\left(\pi r_{2}^{2}-\pi r_{1}^{2}\right)$

Now putting the value of (b) in (a) we get

⟹ 2πh(r1 + r2) + 231 = 4620

⟹ 2π ∗ 7(r1 + r2) = 4389

⟹ π(r1 + r2) = 313.5 ... (c)

Now solving eq (b)

$\pi r_{1}^{2}-\pi r_{2}^{2}=115.5$

$\Rightarrow \pi r_{2}^{2}-\pi r_{1}^{2}=115.5$

$\Rightarrow \pi\left(r_{2}+r_{1}\right)\left(r_{2}-r_{1}\right) \ldots(d)$

Dividing equation (d) by (c) we get

$\frac{\left.\pi r_{1}+r_{2}\left(r_{2}-r_{1}\right)\right)}{\pi\left(r_{1}+r_{2}\right)}=\frac{115}{313.5}$

⟹ r2 − r1 = 0.3684 cm