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प्रश्न
Water in a canal, 6 m wide and 1.5 m deep, is flowing at a speed of 4 km/hr. How much area will it irrigate in 10 minutes if 8 cm of standing water is needed for irrigation?
उत्तर
We have,
Width of the canal, b = 6 m
Depth of the canal, h = 1.5 m,
Height of the standing water needed for irrigation, H=8 cm = 0.08 m,
speed of the flowing water, l=4 km / h `= 4000/60 = 200/3 "m"// "min"`
Now,
Volume of water flowing out from canal in 1 min =lbh
`=200/3xx6xx1.5`
=600 m2
⇒ Volume of water flowing out from canal in 10 min = 600 × 10 = 6000 m3
`"so, the area of irrigation" = "Volume of water flowing out from canal in 10 min"/"Height of the standing water needed for irrigation"`
`= 6000/0.08`
= 75000 m2
= 7.5 hectare (As, 1 hectare = 10000 m2)
Hence, it will irrigate 7.5 hectare of area in 10 minutes.
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Let the radius of the wire by r cm.
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