The difference between inside and outside surfaces of a cylindrical tube 14 cm long, is 88 cm2. If the volume of the tube is 176 cm3, find the inner and outer radii of the tube.
Let the inner and outer radii of the tube be r cm and R cm, respectively.
Length of the cylindrical tube, h = 14 cm
Outer curved surface of the cylinder − Inner curved surface of the cylinder = 88 cm2 (Given)
$\therefore 2 \pi R h-2 \pi r h=88$
$\Rightarrow 2 \times \frac{22}{7} \times 14 \times(R-r)=88$
$\Rightarrow R-r=\frac{88 \times 7}{2 \times 22 \times 14}$
$\Rightarrow R-r=1 \mathrm{~cm} \quad \ldots \ldots(1)$
Volume of the tube = 176 cm3 (Given)
$\therefore \pi\left(R^{2}-r^{2}\right) h=176$
$\Rightarrow \frac{22}{7} \times(R-r) \times(R+r) \times 14=176$
$\Rightarrow R+r=\frac{176 \times 7}{22 \times 1 \times 14} \quad\left[\begin{array}{ll}\text { Using } & \text { (1) }\end{array}\right.$
$\Rightarrow R+r=4 \mathrm{~cm} \quad \ldots \ldots(2)$
Adding (1) and (2), we get
2R = 5
⇒ R = 2.5 cm
Putting R = 2.5 cm in (2), we get
2.5 + r = 4
⇒ r = 4 − 2.5 = 1.5 cm
Thus, the inner and outer radii of the tube are 1.5 cm and 2.5 cm, respectively.