Question

How many cubic meters of earth must be dug out to make a well 28 m deep and 2.8 m in diameter ? Also, find the cost of plastering its inner surface at Rs 4.50 per sq meter. 

 

Answer 1

Radius of the well = `2.8/2=1.4 m`

`"Depth of the well=28 m"`

`"Therefore, volume of earth dug out "=pir^2h`

`=22/7xx1.4xx1.4xx28`

`=17248/100`

`=172.48m^3`

`"Area of curved surface"=2pirh`

`=2xx22/7xx1.4xx28`

`=246.40 m^2`

Cost of plastering at the rate of `Rs.450` per sq m

`=Rs. 2.40xx4.50`

`=RS 1108.80`