This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

As you can see that fifteen matches have been used to form an arrangement. What you have to do is remove any six of them to make them ten.

What is greater than gold but cannot be bought. it can never be sold and can earn if its sought. though it can be broken, it can still be fixed. for by birth it can't start nor by death it is ended.what am i?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

I shave every day, but my beard stays the same. What am I?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

Which word does the below Plexor means ?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

What number comes next in this sequence:
7 8 5 5 3 4 4 _

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?