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

Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

Identify The phrase in the picture.

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

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?

There are 2 cops parked along a one-way street looking for traffic violations. They spot a taxi driver going in the wrong direction, yet they do nothing.

Why?

Things are just as they seem, right? Well, check again.
Can you count the number of tigers in this picture ?

You are given 16 witch hats. The hats are divided in four different colours – red, blue, green and yellow. Every colour has been assigned to four hats. Now each of the hat will be glued with a label of an arithmetic sign – ‘+’, ‘-‘, ‘x’ or ‘/’. But you can label one sign only once on one colour. In such an arrangement, the hats can be uniquely defined by its colour and symbol.

Can you arrange all the 16 hats in a 4x4 grid in a fashion that no two rows and columns have a repetition of colour or sign?
We have arranged four hats in the below picture to assist you.