Q. 245.0( 1 Vote )

# A storage tank consists of a circular cylinder with a hemisphere adjoined on either end. If the external diameter of the cylinder be 1.4 m and its length be 8 m, find the cost of painting it on the outside at the rate of Rs. 10 per m^{2}.

Answer :

The figure is given below:

**Concept Used:**

The curved surface area of a cylinder = 2πrh

The curved surface area of hemisphere = 2πr^{2}

**Given:** External Diameter of the cylinder = 1.4 m

Length of the cylinder = 8 m

Cost of painting on the outside = Rs. 10 per m^{2}

**Explanation:**

Thus r = 0.7m and h = 8m

Total curved surface area of the tank = 2πrh + 2πr^{2}

⇒ Total curved surface area

Therefore, the total surface area of the storage tank is 38.28 m^{2}.

Cost of painting it on the outside at the rate of Rs. 10 per m^{2} =

38.28 × 10 = Rs. 382.80

**Hence, the cost of painting the storage tank from the inside is Rs. 382.80.**

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