Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

How many words can a quill made with the feather of a pigeon write with a 100ml bottle of black ink?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

Using Only Five 5's and any mathematical operator make sum as 37

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

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?

I can be made.
I can be cracked.
I can be told.
I can be played.

Who am I?