13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

The day after tomorrow will be three days before Tuesday. Can you find out what is today?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

What animal walks on four legs in the morning, two legs during the day, and three legs in the evening?

Oedipus, the king of Thebes, figured out the answer to the riddle:

In a boat, the father of a sailor's son is sitting with the son of the sailor. However, the sailor is not present on the boat.

Can this even be possible?