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?

If you drop me I’m sure to crack, but give me a smile and I’ll always smile back. What am I?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

You walk into an old horror house. It has no power or plumbing. Once inside, you see three doors. Each door has a number on it. Behind each door is a way for you to die. Behind door number one, you die by getting eaten by a lion. Behind door number two, you die by getting murdered. Behind door number three, you die by an electric chair. You can’t turn back, so you have to go through a door. Which door do you go through?

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?”

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

There are four 3-link chains. All you have to do is join them into a big 12-link chain. For joining two closed links, one of the links must be cut and placed onto the other link for closing.

How many minimum links will you have to cut to make the big chain?

What does man love more than life, and hate more than death or mortal strife; that which satisfied men want; the poor have, and the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?