**Question:**

30 circular plates, each of radius 14 cm and thickness 3 cm are placed one above the another to form a cylindrical solid.

Find

- the total surface area.
- volume of the cylinder so formed.

**Solution:**

Given, radius of a circular plate, r = 14 cm

Thickness of a circular plate = 3 cm

Thickness of 30 circular plates = 30 x 3 = 90 cm

Since, 30 circular plates are placed one above the another to form a cylindrical solid. Then, Height of the cylindrical solid, h = Thickness of 30

circular plates = 90 cm

- Total surface area of the cylindrical solid so formed

= 2πr(h+ r)=2 x (22/7) x 14(90+ 14)

= 44 x 2 x 104 = 9152 cm2

Hence, the total surface area of the cylindrical solid is 9152 cm2, - Volume of the cylinder so formed = πr2h

= (22/7) (14)2 x 90 =(22/7) x 14 x 14 x 90

= 22 x 28 x 90 = 55440 cm3

Hence, the volume of the cylinder so formed is 55440 cm3.