here is a collection of some of my favourite brain teasers:

1. There are two poles on the surface of a lake. A bird is sitting on top of one of them. The bird takes off from the first poles grazes the surface of water and ends up on the second pole. What is the shortest path the bird should take in order to minimize the distance travelled. Length of the poles are 10 ft and 8 ft above the surface of the water and the  distance between the poles is 30 feet. (hint: the dimesions are irrelevant)

2. A govt official is conducting a census survey. He visits a family of four. A mother and 3 daughters. The official asks the mother to about her daughters ages. Being a cryptologist the mother replies: "If you multiple my daughter's ages you will get 36". The official is puzzled: "Sorry ma'am but sufficient information isn't sufficient". To this the mother replies: "If you add all my daughter's ages the number you get is same as my neighbours apt number". The official quickly browses his records to check the neighbours apt number. After doing some calculations he is still exasperated: "I am still unable to figure out your daughter's ages". The lady gives him a last hint: "My eldest daughter has blue eyes !". The official replies: "I have all the information I need now. Have a good day". So how old are the daughters ?

3. What is the remainder when you divide 5 to the power 99 by 13 ?

4. Evaluate 4444 to the power 4444. One should get a very large number. Add all the digits of this large number     you should get another number. Add all the digits of this number and you should get yet another number. Continue     doing this until you are left with a single digit. What is digit is this ?

5. How can you swap two integers without the use of a temporary variable in a C program ?
    eg. int a,b;
         int temp;
         temp = a; a = b; b = temp; (This is NOT allowed)

6. A sheik is making a will. He has two sons and a large fortune. His sons each have a camel of their own. The sheik says : "There is a town about 100 miles from here. Whose evers camel is the slowest gets all the inheritance. So the sons hop on to their respective camels and head towards the town. However, due to the conditions imposed; end up just circling around and come to a deadlock where none is willing to move. Finally they meet a wise man in the desert who solves the dilemna by whispering to them the solution. The moment they hear the solution both the sons get on the camels and head towards the town as fast as possible. What did the wise man say to them ?

7. There are "n" number of gas stations on a circular route. The total amount of gas in all the gas station is just enough to make one trip around the route. Some of the gas stations may not have any gas at all. You must prove that there is ATLEAST one gas station where one can start the trip and return to the same station.

8. This one I have borrowed from the entrance exam I had to take for IIT Bombay(my undergraduate school): if (x*x+y*y) = 1 and (a*a+b*b) = 1 then prove that -1 <= (a*x+b*y) <= 1

9. Here is another one I have borrowed from the same entrance exam: "there are four ants sitting at four corners of a square table 1 meter in dimension. At some point all the ants simultaneously start moving towards the ant to the right at a constant velocity. Of course after a point they are all going to converge at the center of the table. What distance does each ant travels ?"

more to come ->

send answers to mraje@mailcity.com

For solutions email to: mraje@mailcity.com