Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

The doctor prescribed you to take one pill from the bottle every half an hour. The bottle is now left with only three pills.

How long do you think you have before you run out of pills?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

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?

Find the missing number in the image below.

What number divided by 4 is the same as that number minus 4?

Sahir enters the bank aims to rob and finds Jai standing inside armless. He aims a gun at him and asks him the code for the safe. Jai says, 'The code is different every day but if you hurt me, you will never get to know the code'.

Sahir pins him down and ties him with a rope. He then inserts the safe code and easily takes all the money with him.

How did he know the code?

Three logicians went to bar for having a drink. The bar person asks the logicians "Do they all want to have the drink?". The first logician replied, " I don't know". The second logician replied, " I don't know". What is the reply of the last logician?

Can you find out the number that should replace the question mark with a valid reason?