A well with 14 m inside diamet er is dug 10 m deep. Earth tak en out of it has been
evenly spread all around it to a w idth of 21 m to fo rm an embank ment. The height of
the embank ment is:
(a) 1/2 m (b) 2/3 m (c) 3/4 m (d) 3/5 m

• the volume of sand dig out(volume of well)=volume of embankment formed which is of a hallow cylindrical shape
  usually both are cylindrical in shape so volume= pi* radius^2* height(or depth)
  since width(radius) of embankment which is out side the well=21
  so total radius of cone formed by embankment=21+7(that is inside well)=28
  =>pi*7*7*10=[(pi*28*28*h)-(pi*7*7*h)]
  =>490=h*(28^2-7^2)
  =>h=490/[(7*4)^2-7^2]
  =>h=490/[7^2*(4^-1)]
  =>h=490/[49*15]
  =>h=10/15=2/3 mts...
  so option (b)...
• 12 years agoHelpfull: Yes(13) No(0)
• http://www.emathzone.com/tutorials/geometry/hollow-circular-cylinder.html
  
  read this was a great help
• 12 years agoHelpfull: Yes(3) No(0)
• total earth dug=14*10=140
  
  21 earth=1/10m
  140 earth=?
  
  14/21=2/3
  B
• 12 years agoHelpfull: Yes(2) No(0)