Interesing puzzles

1. Train from station A takes 2 hrs to reach station B. Train from station B takes 1 hr to reach station A. Both trains starts at same time. After how many minutes they meet each other?(of course they are running on parell tracks)
2. There are some coins on the top of a table in a dark room. Among those coins only 11 coins showing HEAD on the top, rest is showing TAIL. Can you divide those coins in to two groups, in such a way they contains equal number of HEADs. Hint: Two groups may contain un equal number of coins and you can flip as many coins as you want. zero is also a number so u can flip all the heads and divide in to two groups.
3. A bacteria doubles itself in 3 mins. It took 3 day and 33 mins to fill 100 ml glass bottle. How much time it will take to fill half of the bottle?( very trivial)
4. How will you get 24 by using the numbers 1,4,5, and 6. Rules: you can use any mathematical operation like +,-,x and / any number of times. You must use all the four numbers only once. combination of numbers are not allowed like u cant take 1 and 4 as 14. You can use as many brackets as u want.
5. Magical basket: There was a person with a magical basket. When ever he opens it, what ever inside is doubled. One day he was walking with the basket keeping some apples inside. He saw a poor man, so he opened his basket and gave him some apples. Then he continued, he found another poor man, so he opened his basket and gave him number of apples. Like that he gave equal number of apples to 5 poor men and at the end he left nothing in the basket. Question: How many apples he initially had? and how many he gave to each poor man?
6. A generalized question(from the previous problem), suppose he has to offer equal number of apples to 'n' poor men, how many apples he should initially have? and how many he has to offer each poor man?
7. Train from A takes 24hrs to reach B. Train from B takes 24hrs to reach A. Every one hr, there is a train starting from A towards B, similarly every one hr a train staring from B towards A.The question is for a train starting from A, how many trains it will cross in the opposite direction during the whole journey?
8. A man lives on the tenth floor of a building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator - or if it was raining that day - he goes back to his floor directly. Otherwise, he goes to the seventh floor and walks up three flights of stairs to his apartment. Can you explain why?
9. How can you throw a ball as hard as you can and have it come back to you, even if it doesn't hit anything, there is nothing attached to it, and no one else catches or throws it?
10. Now physics one:You are in a room where there are no metal objects except for two iron rods. Only one of them is a magnet. How can you identify this magnet?
    

to be continued...