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प्रश्न
In the middle of a rectangular field measuring 30m × 20m, a well of 7 m diameter and 10 m depth is dug. The earth so removed is evenly spread over the remaining part of the field. Find the height through which the level of the field is raised.
उत्तर
Let r m be the radius and h m be the depth of the well that is dug.
Volume of the well = `pi` r2h = `22/7` × (3.5 m)2 × (10 m) = 385 m3
Volume of the well = Volume of the rectangular field
Volume of the rectangular field = 385 m3 = 30 m × 20 m × height
\[\text{ Height }= \frac{385 {m}^3}{30m \times 20m} = 0 . 641 m = 64 . 1 cm\]
Hence, the height through which the level of the field is raised is 64.1 cm.
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