Find the hidden tiger in the given optical illusion ?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

81 x 9 = 801. What must you do to make the this equation true?

It belongs to you, but other people use it more than you do. What is it?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

What kind of tree can you carry in your hand?

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.

Why Aeroplane windows are round?

Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?