The length of a metal hollow cylinder is $70\, cm$. If the radius of the hollow inside it is $10\, cm$ and the metal thickness is $1\, cm$,find the difference between the areas of the outer and inner curved surfaces.

$(440 \ cm^2)$ For a metal hollow cylinder: height $(h) = 70\, cm$.
Inner radius $(r) = 10\, cm$.
Outer radius $(R) = \text{Inner radius} + \text{Thickness of metal} = 10 + 1 = 11\, cm$.
The difference between the areas of the outer and inner curved surfaces is given by:
$\text{Difference} = 2\pi Rh - 2\pi rh = 2\pi h(R - r)$.
Substituting the values:
$\text{Difference} = 2 \times \frac{22}{7} \times 70 \times (11 - 10) = 2 \times 22 \times 10 \times 1 = 440\, cm^2$.