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Question
In the middle of a rectangular field measuring 30 m × 20 m, 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.
Solution
Radius of dug `= 7/2 m`
Depth of dug = 10 m
The volume of dug
`= pi(7/2)^2 xx 10`
`= 22/7 xx 49/4 xx 10`
The volume of dug = 385 m3
Let the height through which the level of the field is raised will be x.
But, volume of dug = volume of earth spread over field.
`385 = 30 xx 20 xx x `
`x = (385) / (30 xx 20)`
`x = 68.6cm`
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Assertion (A)
If the radii of the circular ends of a bucket 24 cm high are 15 cm and 5 cm, respectively, then the surface area of the bucket is 545π cm2.
- Reason(R)
If the radii of the circular ends of the frustum of a cone are R and r, respectively, and its height is h, then its surface area is - Both Assertion (A) and Reason (R) are true and Reason (R) is a correct explanation of Assertion (A).
- Assertion (A) is true and Reason (R) is false.
- Assertion (A) is false and Reason (R) is true.
The curved surface area of a right circular cone is 12320 cm2. If the radius of its base is 56 cm, then find its height.
