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 = πr²h

`= 22/7 xx 1.4 xx 1.4 xx 28`

`= 17248/100`

= 172.48 m³

Area of curved surface = 2πrh

`= 2 xx 22/7 xx 1.4 xx 28`

= 246.4 m²

Cost of plastering at the rate of ₹ 4.50 per sq m.

= ₹ 246.40 × 4.50

= ₹ 1108.80