Find The Next Number in this series.
1, 2, 6, 42, 1806 ?

A chess tournament is taking place on knock-out terms (the one who loses the match is out of the game).
(a) If 10 matches are played in total, how many players participated?
(b) If 20 players took part in the tournament, how many matches were played?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

In case you were starting to feel confident, this one was meant for third graders in Vietnam. The answer is 66, but we don't blame you for scratching your head about how they got there.

A word I know has six letters it contains, remove one letter and 12 remain. What is it?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

Astrology starts with the alphabet A, Biology starts with B, Psychology with P and Limnology with L.

Can you find an "ology" that begins with a P?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?