Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

In a town, there are over 100 flats.
Flat-1 is named first flat.
Flat-2 is named second flat.
Flat-3 is named third flat.

A visitors 'Victor' decides to walk through all the flats, he finds all the flats except flat-62.
Victor later founds that the local of the town have given it another name.

What is the name of the Flat?

Why is a river so rich ?

Can you name some countries which do not have the alphabet 'A' in them?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

How many triangles can you find in this given picture?

Whats the next number in the below number sequence pattern.

A professor thinks of two consecutive numbers between 1 and 10.
'A' knows the 1st number and 'B' knows the second number

A: I do not know your number.
B: Nor do I know your number.
A: Now I know.

What are the four solutions for this?

Using Only Five 5's and any mathematical operator make sum as 37

There are forty elephants and they have forty-fore heads. How can this be possible?