A tank can be f ill ed by t wo pipes in
20 minutes and 30 minutes respectively.
When the tank was empty, the two pipes
were opened. After some time, the first pipe
was stopped and the tank was filled in
18 minutes. After how much time of the
start was the first pipe stopped ?
A hare sees a dog 100 metres away from
her and scuds off in the opposite direction
at a speed of 12 km per hr. A minute later
the dog perceives her and chases her at a
speed of 16 km per hr. At what distance from
the spot dog will overtake the hare when
the hare took flight ?
A train met with an accident 3 hours after
starting, which detains it for one hour, after
which it proceeds at 75% of its original
speed. It arrives at the destination 4 hours
late. Had the accident taken place 150 km
further along the railway line, the train
would have arrived only
hours late. Find
the length of the trip and the original speed
of the train