A right-angled ΔABC with sides 3 cm, 4 cm and 5 . . .

Question : A right-angled ΔABC with sides 3 cm, 4 cm and 5 cm is revolved about the fixed side of 4 cm. Find the volume of the solid generated. Also, find the total surface area of the solid. 

Doubt by Saksham

Solution : 

When the Right Triangle is rotated with about 4 cm side then the resulting figure will be a solid cone of radius 3 cm, height 4 cm and slant height 5 cm.

r = 3 cm

h = 4 cm

l = 5 cm

Volume of the solid
= Volume of the cone
= (1/3)πr²h

= (1/3)π(3)²(4)
= 12π cm³

Total Surface area of the solid

= Total surface area of the cone

= πr(l+r)

= π(3)(5+3)

= π(3)(8)
= 24π cm²