Get this one, You find yourself stranded on a lonesome road because your car broke due to a massive snow storm, you use your celphone to find that help will only come on the morning after and to make situation worst your down to your last cigarrete. As night settles you realise that spending the night inside the car would be suicide because it gets awfully cold. Thats when you spot an abandoned cabin a few meters ahead, as you enter you find a few candles, an old fire wood stove and a huge fire place. Whats the first thing you must light?
Something to do with the cigarette perhaps. You mentioned nothing about having anything to created a light. Don't cars have cigarette lighters?
I see a thing. Of this thing I know these three:
1) The man who makes this will sell it.
2) The man who buys this will not use it.
3) The man who uses this will not know it.
What do I see?
What's the next number?
1
11
21
1211
111221
?
What about my tennis ball problem?
One of twelve tennis balls is a bit lighter or heavier (you do not know which) than the others. How would you identify this odd ball if you could use an old two-pan balance scale only 3 times?
You can only balance one set of balls against another, so no reference weights and no weight measurements.
Reflection principle. Split them into two groups, and turn all six coins from one of the groups over.