How can you make number one disappear by adding something to it?

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?”

What three numbers, none of which is zero, give the same result whether they’re added or multiplied?

Next Number in the Series,

5, 16, 49, 104, ?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

A word I know has six letters it contains, remove one letter and 12 remain. What is it?

It is raining today at 11:59 am. What is the probability of sunny weather after 72 hours?

I make two people out of one. What am I?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

Through your logical capabilities, can you make 7 an even?