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?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

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?

What is the riddle which can be asked all day with a different correct answer each time.

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

Can you spot the man between the coffee bean in the picture below ?

You can take four of the five letters out of this word, but the pronunciation never changes. What is the word?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

How can one talk without saying a single word?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?