I make two people out of one. What am I?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

I have two coins.
* One of the coins is a faulty coin having a tail on both sides of it.
* The other coin is a perfect coin (heads on side and tail on other).

I blindfold myself and pick a coin and put the coin on the table. The face of the coin towards the sky is the tail.

What is the probability that another side is also tail?

How many triangles can you find in this given picture?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

What have one eye but still cannot see?

Which is Odd One Out and why?

4377

3954

9862

8454

9831

What goes through cities and fields, but never moves?

Why Wine Glass Stem is so long?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?