2. You have two sand watches, one of 7 minutes and the other one
of 4 minutes, now you want to measure 9 minutes, how do you do
it?
3. You have two ropes and a lighter, each rope burns in exactly 60
miutes, and not lineraly (meaning that some parts of the rope burn
faster than another part), you want to measure 45 minutes, how do
you do it? This one is beautiful, it took me some time to solve
it.. the answer suddenly popped in my mind when i was driving my
car toward home!
4. You have three cups, one of 5 liters, one of 3 liters, and one
of unlimited place (assume we live on an extraterrestial planet
where such cups exists), we also have an unlimited supply of water.
We want to have exactly 4 liters in the unlimited cup, how do you
do it? This one is quite easy but still nice.
5. You have 8 bags full of pieces of gold. In 7 of the bags, each
piece weight exactly 1 gram, while in the other bag, each piece
weight exactly 0.9 gram. You don't know which bag is which (of
course), how do you find out which bag is the one with the lighter
pieces when you have only one possibility of weighting using an
electronic weighting device.
