You have 10 boxes of balls (each ball weighing exactly10 gm) with one box with defective balls (each one of the defective balls weigh 9 gm). You are given an electronic weighing machine and only one chance at it. How will find out which box has the defective balls?
100 prisoners are stuck in the prison in solitary cells. The warden of
the prison got bored one day and offered them a challenge. He will put
one prisoner per day, selected at random (a prisoner can be selected
more than once), into a special room with a light bulb and a switch
which controls the bulb. No other prisoners can see or control the light
bulb. The prisoner in the special room can either turn on the bulb,
turn off the bulb or do nothing. On any day, the prisoners can stop this
process and say â€œEvery prisoner has been in the special room at least
onceâ€. If that happens to be true, all the prisoners will be set free.
If it is false, then all the prisoners will be executed. The prisoners
are given some time to discuss and figure out a solution. How do they
ensure they all go free?
How many points are there on the globe where, by walking one mile south,
then one mile east and then one mile north, you would reach the place
where you started?