Why do you find that most of the buildings are deprived of the 13th floor?

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

Can you count the number of triangles in the given figure?

What does the below image rebus riddle means ?

Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

Can you identify the hidden rebus in the image below?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Can you find out the remainder when 3^300 is divided by 5?

What building has the most stories?

Find the next number in the following series:
6, 14, 26, 98, __?