There are two bottles that consists of different pills each. You must take the two pills at the same time and if you forget, or just take one of them or take two of the same kind, you will die a miserable death. In a hurry, you pour from both the bottles at the same time and three pills fall down in your hand.
Now you can’t throw away the pills as they are quite rare to be found. Also both of the pills look exactly the same and have all the characteristics similar. How will you ensure that you don’t take a wrong pill and die ?
All you have to do is labelling the pills as A and B. Now when you draw out three pills, you will either have 3A or 2A 1B or 1A 2B or 3B. Now if all the pills are from same bottle you can simply take another from the other bottle. If some other combination comes out, you can manage by filling in from the required bottles.
