Q. 373.7( 6 Votes )

# A right angled triangle whose sides are 3 cm, 4 cm and 5 cm is revolved about the sides containing the right angle in two ways. Find the difference in volumes of the two cones so formed. Also, find their curved surfaces.

Answer :

Height of the cone (h_{1})=3 cm

Radius of the cone (r_{1}) = 4 cm

Slant height of the cone (l_{1}) = 5 cm

Volume of cone (V_{1})=

cm^{3}

cm^{3}

Again after rotating

Height of the cone (h_{2})=4 cm

Radius of the cone (r_{2})=3 cm

Slant height of the cone (l_{2})=5 cm

Volume of cone (V_{2)}

cm^{3}

cm^{3}

Difference between the volume two cones =16π – 12π

= 4π cm^{3}

Curved surface area of first cone =π × r_{1}× l_{1}

= π × 4 × 5

= 20 cm^{2}

Curved surface area of second cone = 15 cm^{2}

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