Why is a river so rich ?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

Can you place six X (crosses) in below board without making three in a row in any way ?

What makes this number unique: 8,549,176,320?

Replace the 'X' with any mathematical symbol to make the expression equal to 111.

18 X 12 X 2 X 3 = 111

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

A swan sits at the center of a perfectly circular lake. At an edge of the lake stands a ravenous monster waiting to devour the swan. The monster can not enter the water, but it will run around the circumference of the lake to try to catch the swan as soon as it reaches the shore. The monster moves at 4 times the speed of the swan, and it will always move in the direction along the shore that brings it closer to the swan the quickest. Both the swan and the the monster can change directions in an instant.
The swan knows that if it can reach the lake's shore without the monster right on top of it, it can instantly escape into the surrounding forest.

How can the swan successfully escape?

What is black when you buy it, red when you use it, and gray when you throw it away?

Identify Me

Hint1: I am a god
Hint 2: I am a planet
Hint 3: measurer of heat

An artist while painting a scenic beauty, decides to paint three layers of blue colour on the sky.

Which layer will go on the first?