Solution:

987,654

Let us assume with a smaller number and then increase the number by extrapolating. If there are two citizens, the number of hairs on their heads will be zero and one. Therefore for ‘n’ number of citizens, the hair distribution will range from 0 to (n-1).

If you take up a case of a number greater than 987,654 let’s say 987,655; and consider the fact that none of the citizens have 987,654 hairs and they must be having different number of hairs, one must be having more than 987,654 hairs which is bluntly violating the fact of the town that there are more citizens than the hairs on any individual.

Solution:

16-days

In 15-days, he will climb 15-inch and when he climbs 5 inch more, he will be out of the well :-)

Solution:

The clerk said that every day the password is CHANGED. Changed is the password.

Solution:

First fill the 8 liters jug complete - 4, 8, 0
Fill the 5 liters jug with 8 liters jug - 4, 3, 5
Pour back the beer from 5 liters jug to 12 liters jug - 9, 3, 0
Pour the 3 liters from 8 liters jug to 5 liters jug - 9, 0, 3
Fill the 8 liters jug completely from 12 liters jug - 1, 8, 3
Fill the 5 liters jug from the 8 liters jug - 1, 6, 5
Pour the entire 5 liters jug back in 12 liters jug - 6, 6, 0

You have successfully split the beer into two equal parts.

Solution:

Rhea will open just one present.
Cindy|Y - Y is the 25th alphabet
Duk|E - E is the 5th alphabet
Joh|N - N is the fifteenth alphabet
Rhe|A - A is the first alphabet

Solution:

The Bangladeshi seaman is the thief. This is because the Japanese flag cannot be identified as upside down as it is the same both ways. Thus he is just trying to escape the situation.

Solution:

Six.

There are only five colors, so six socks guarantee that two will be the same color.

Solution:

Align the toothpicks to form TEN. Use one toothpick for each of the lines.

Solution:

36 meters.

100/v1 = 80/v2
100/v2 = 80/v3

20+(20/v2)*v3=20+16 = 36

Solution:

Step one: First you will have to make 3 trips of 1,000 apples 333 miles. Then you will be left with 2,001 apples and 667 miles to go.

Step two: Next you will have to take 2 trips of 1,000 apples 500 miles. In this manner you will be left with 1,000 apples and 167 miles to go (you have to leave an apple behind).

Step three: At last, you will have to travel the last 167 miles with one load of 1,000 apples and you will be left with 833 apples when you reach the town

Solution:

I filled a glass full of water and held it over my head for 20 minutes.