I can write cow in 13 letters.

Can You?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

How far can you walk into the woods?

You have a thousand Re. 1 coins with you. You have ten bags with you and you can put any number of coins in each of the bags. The condition is that if someone asks you for any amount between 1 and 1000, you must be able to give that amount by just giving the bag (you are not allowed to open the bag and give coins).

How will you do it?

Your last good ping-pong ball fell into a narrow metal pipe embedded one foot deep in concrete.
How can you get it out undamaged, if all the tools you have are your tennis paddle, shoe laces, and plastic water bottle, which does not fit into the pipe?

Can you find out the missing number in the grid?

What is wrong in the below Picture?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

A red house is made out of red bricks. A yellow house is made out of yellow bricks. And, a blue house is made out of blue bricks. So, what is a greenhouse made of?