How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

Why is 6 afraid of 7?

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

I am quite hot but become too cold if you remove the first two letters. What am I?

Can you place six X (crosses) in below board without making three in a row in any way ?

In a supermarket, there is an intelligent glass pane before a refrigerating unit. This glass pane allows cherries and apples through it but does not allow grapes and Orange to pass through it.

Can you identify the rule that the glass pane is following?

You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple.
Now all your friends have one apple each, yet there is an apple remaining in the basket.
How?

There's one "sport" in which neither the spectators nor the participants know the score or the leader until the contest ends.

What is it?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?