# Find the cost of plastering

A well has to be dug that is to be 22.5 m deep and of diameter 7 m. Find the cost of plastering the inner curved surface at Rs.4 per sq metre:

- Rs. 1690
- Rs. 1875
- Rs. 1980
- None of these

**Answer: (3) 1980**

**Explanation:-**

The deep of the well = 22.5 m

The diameter of the well = 7 m

Therefore, the radius of the well = 7/2 = 3.5 cm

Then, the curved surface area of the well = 2 x 22 x 7 x 22.5/7 x 2

= 22.5 x 22

= 495 sq. m

The cost of plastering the inner curved surface at Rs.4 per sq meter

Then, the total cost of plastering the inner curved surface of the well = 495 x 4

= Rs. 1980.

Hence, the correct answer is option (3) Rs. 1980.