Find the value of "?" in the ball picture Riddle below:

What is black when you buy it, red when you use it, and gray when you throw it away?

A rubber ball keeps on bouncing back to 2/3 of the height from which it is dropped. Can you calculate the fraction of its original height that the ball will bounce after it is dropped and it has bounced four times without any hindrance ?

Which Travels Faster? Solve below famous picture riddle:

Count the number of triangles in the below picture?

You are given four tennis balls and asked to arrange those balls in a manner that the distance between each one of them is exactly equal. How will you do it?

What occurs twice in a week, once in a year but never in a day?

What can go up a chimney down, but can’t go down a chimney up?

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?

Who always enjoys poor health?