When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

The captain of a ship is telling you an interesting story and then poses a question. He says, “I have travelled the oceans far and wide. One time, two of my sailors were standing on opposite sides of the ship. One was looking west and the other one east. And at the same time, they could see each other clearly. Can you tell me how that was possible?”

Can you place three balls such that the equation shown in the picture holds true?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

I have holes on the top and bottom. I have holes on my left and on my right. And I have holes in the middle, yet I still hold water. What am I?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

How many letters are in the alphabet?

Can you find the mistake in the below statement?