How many points are there on the globe where, by walking one mile south, then one mile east and then one mile north, you would reach the place where you started?

An equation has been laid down using a few matchsticks. However, as you can see, the equation is not correct. Can you correct the equation if you are allowed to add or remove 5 matchsticks?

When monkey rotate the gear, which mark will be hit 1 or 2 ?

10 people came into a hotel with 9 rooms and each guest wanted his own room. The bellboy solved this problem.
He asked the tenth guest to wait for a little with the first guest in room number 1. So in the first room, there were two people. The bellboy took the third guest to room number 2, the fourth to number 3, ..., and the ninth guest to room number 8. Then he returned to room number 1 and took the tenth guest to room number 9, still vacant.
How can everybody have his own room?

You can hear me, but you can't touch or see me.

What am I?

There are nine dots in the picture that has been attached with this question. Can you join all the dots by drawing four straight lines without picking up your pen?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

In the image given, you can find several triangles. Can you count them all?

How can you take 2 from 5 and leave 4?

How many letters are in the alphabet?