2, 3, 5, 9, 17, _ What is the next number in the sequence?

The more of this there is, the less you see. What is it?

A 52% bias toss for head using the 51% tail bias coin was done to obtain a fair result.

Can you find how bias is the floor in this case?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?

Move four matchsticks to the below square to form three squares?

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).

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

In a classic wine shop, the list of three most popular wines are:
- The cost of 1 French wine bottle: 500$
- The cost of 1 German wine bottle: 100$
- The cost of 20 Dutch wine bottles: 100$

John entered the wine shop and he needs to buy
- All three types of wine bottles.
- Needs to buy Dutch wine bottles in multiples of 20.
- Need to buy 100 wine bottles in total.

John has only 10000$. How many wine bottles of each type, John must buy?

What is harder to catch the faster you run?