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Question
A 16m deep well with diameter 3.5m is dug up and the earth from it is spread evenly to form a platform 27.5m by 7m. Find height of platform?
Solution
Let as assume well is a solid right circular cylinder
us of cylinder(r) = 3.5/2 = 1.75m
Height (or) depth of well = 16m.
Volume of right circular cylinder = πr2h
= `22/7` x (1.75)2 X 16 .............(1)
Given that length of platform(l) = 27.5m
Breath of platform (b) = 7cm
Let height of platform be xm
Volume of rec tan gle = lbh
= 27.5 x 7 x `x`= 192.5`x` ..........(2)
Since well is spread evenly to form platform
So equating (1) and (2)
V1 = V2
⇒` 22/7`(1.75)2 x 16 = 192.5`x`
⇒ `x`= 0.8m
∴ Height of platform(h) = 80cm.
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