# (i) 30 circular plates, each of radius 14 cm and thickness 3cm are placed one above the another to form a cylindrical solid. Find : the total surface area(ii) 30 circular plates, each of radius 14 cm and thickness 3cm are placed one above the another to form a cylindrical solid. Find volume of the cylinder so formed.

(i) Answer  : $9152\; cm^{2}$

It is given that 30 circular plates are placed one above the other to form a cylindrical solid.

So we can see that the height of this cylindrical solid = total thickness of 30 circular plates placed one over the other

Given, thickness of one circular plate $=3\; cm$

Thickness of 30 circular plates $=30 \times 3 = 90\; cm$

Now, radius of circular plate, r = 14 cm

We know that

Total surface area of the cylindrical solid of formed will be equal to $2\pi r\left ( h+r \right )$

Where r is its radius and h is the height. So, putting the above calculated values:

Total surface area       $=2 \times \frac{22}{7}\times 14\left ( 90+14 \right )$

$=44 \times 2\times 104$

$=9152\; cm^{2}$

Hence, the total surface area of the cylindrical solid is $9152\; cm^{2}$.

(ii)

Answer : $55440\; cm^{3}$

It is given that 30 circular plates are placed one above the other to form a cylindrical solid.

So we can see that the height of this cylindrical solid = total thickness of 30 circular plates placed one over the other

Given, thickness of one circular plate = 3 cm

Thickness of 30 circular plates $=30 \times 3=90\; cm$

Now, radius of circular plate, r = 14 cm

We know that

Volume of the cylinder so formed will be equal to $\pi r^{2}h$

Where r is its radius and h is the height. So, putting the above calculated values:

Volume of the cylinder $=\frac{22}{7}\times (14)^{2}\times 90$

$=\frac{22}{7}\times 14\times 14 \times 90$

$=55440\; cm^{3}$

Hence, the volume of the cylindrical solid is $55440\; cm^{3}$

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