Question

If the radii of a frustum of a cone are 7 cm and 3 cm and the height is 3 cm, then the curved surface area is ..... cm².select a proper option (a), (b), (c) or (d) from given options so that the statement becomes correct.
(a) 50????
(b) 25????
(c) 35????
(d) 63????

Answer 1

Mistake in the Question.

Question : If the radii of a frustum of a cone are 7 cm and 3 cm and the height is 3 cm, then the curved surface area is ..... cm².select a proper option (a), (b), (c) or (d) from given options so that the statement becomes correct.

(a) 50π

(b) 25π

(c) 35π

(d) 63π

SOLUTION :

Option (a )is Correct - 50π

Given :

Let the radius of frustum of a cone are r1 & r².

r1 = 7 cm, r² = 3 cm, h = 3 cm

Slant height (l) = √(r1 - r2)² + h²

l = √(7 - 3)² + 3²

l = √4² + 3² = √16 + 9 = √25 = 5

Curved surface area of the frustum of a cone= πl (r1 + r2)

= π×5 (7+3) = 5π×10 = 50π

CSA of the frustum of a cone = 50 π cm²

Hence, the CSA of the frustum of a cone = 50 π cm²

HOPE THIS ANSWER WILL HELP YOU...

Answer 2

Your Options should be:

$(a) 50\pi$

$(b) 25\pi$

$(c) 35\pi$

$(d) 63\pi$

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Given Radius of the bigger cone R1 = 7 cm.

Given Radius of the smaller cone r = 3 cm.

Given Height of the cone h = 3 cm.

Slant height l = $\sqrt{h^2 + (R - r)^2}$

$= > \sqrt{3^2 + (7 - 3)^2}$

$= > \sqrt{9 + 16}$

$= > \sqrt{25}$

$= > 5$

Hence, the slant height of frustum l = 5cm.

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Curved surface area of frustum = $\pi (R + r) * l$

$= > \pi (7 + 3) * 5$

$= > \pi (10) * 5$

$= > 50\pi$

Therefore, the curved surface area of frustrum = $50\pi$

Hope this helps!