Find the cost of sinking a tubewell 280 m deep, having diameter 3 m at the rate of Rs 3.60 per cubic metre. Find also the cost of cementing its inner curved surface at Rs 2.50 per square metre.

#### Solution

Given data is as follows:

Height of the tube well = 280 m

Diameter = 3 m

Rate of sinking the tube well = Rs.3.60/m^{3}

Rate of cementing = Rs.2.50/m^{2}

Given is the diameter of the tube well which is 3 meters. Therefore,

`r = 3/2`m

Volume of the tube well = `pir^2h`

= `22/7 xx 3/2 xx3/2xx280`

= 1980 m^{2}

Cost of sinking the tube well = Volume of the tube well × Rate for sinking the tube well

=1980 × 3.60

= Rs. 7128

Curved surface area = `2pirh`

= `2 xx 22/7 xx 3/2 xx 280 `

=2640 m^{2}

Cost of cementing = `"Curved Surface Area " xx " Rate of cementing"`

= 2640 × 2.50

= Rs.6600

Therefore, the total cost of sinking the tube well is Rs.7128 and the total cost of cementing its inner surface is Rs.6600.