How can you take 2 from 5 and leave 4?

A sundial has the fewest moving parts of any timepiece. Which has the most?

I’m tall when I’m young, and I’m short when I’m old. What am I?

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

What is the coolest letter in the alphabet?

A boy collects white seashells from the sea and brings them home every night. When he has enough of them, he decides to sell them to a trader.

The trader is ready to buy the shells and he asks the boy about the quantity. At this, the boy starts calculating. He has a giant box that contains 3 mini boxes. Two of them have another mini box inside. If the giant box can hold 50 shells, how many brown shells can he sell to the trader?

John buys rice at Rs.60/kg from Britain and then sells them at Rs.5/kg in India. As a result of this, he becomes a millionaire. How come?

Complete the table series riddle by finding the number that can replace "??".

I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but water kills me. What am I?