Question

A solid object in the shape of a double cone is traced by rotating a right-angled triangle of smaller sides 12 cm and 5 cm about the hypotenuse of the triangle. Find the cost (to the nearest rupee) of painting it's surface at the rate of Rupees 3.50 per cm ^2.


Please answer ! It's a request to all the users specially to the Maths Aryabhata and @rvchaudhary Plsss urgent help!!
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Answer 1

Given:

A solid object in the shape of a double cone is traced by rotating a right-angled triangle of smaller sides 12 cm and 5 cm about the hypotenuse of the triangle.  

To find:

Find the cost (to the nearest rupee) of painting it's surface at the rate of Rupees 3.50 per cm ^2.

Solution:

Draw a perpendicular BD to AC, Let BD = h

∴ Area of ABC = 1/2 (12 × 5) = 30

Area of ABC with base AC and height BD = 1/2(h × 13) = 30

⇒ 1/2(h × 13) = 30

⇒ h × 13 = 60

∴ h = 60/13

⇒ BD = 60/13 cm.

So the area = π(AB × BD) + π(BC × BD)

= π(12 × 60/13) +π(5 × 60/13)

= 246.59cm²

As the rate is given as 3.50/cm^2, so we have,

The total cost = 246.59 × 3.50 = Rs. 863.06

Answer 2

Answer:

I hope this is useful for Every one