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?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

The ages of a father and son add up to 66.
The father's age is the son's age reversed.
How old could they be?
(3 possible solutions).

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

Remove two matchsticks to make the below equation correct.

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

I have a head like a cat and feet like a cat, but I am not a cat. What am I?

You have two rectangular wires.

Both of them have property that when you light the fire from one end , it will take 60 minutes to get completely burn.

However, they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could you measure 45 minutes ?