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प्रश्न
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.
बेरीज
उत्तर
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`
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