| | Question 44

The height of a conical tank is 12cm and the diameter of its base is 32cm. The cost of painting if from outside at the rate of Rs 21 per sq. cm. is
(A) Rs 21210
(B) Rs 11120
(C) Rs 22220
(D) Rs 21120

Answer: (D)
Explanation:
We have to find slant height(l) of the cone.
Radius of cone = 32/2 = 16 cm
l = √(r² + h²)
l = √(16² + 12²)
l = √400 = 20 cm
Cost of painting = Surface area of cone x 21
= πrl x 21
= 22/7 x 16 x 20 x 21
= 21120
Hence, the cost of painting is Rs 21120.
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