Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

It's a test that will check your IQ.

Suppose you have one 11 minute hourglass and one 13 minute hourglass.

Can you measure exactly fifteen minutes using them ?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

I am Huge on Sunday and Saturday.
I am small from Tuesday to Thursday.
I do not exist on Monday and Friday.
Who am I?

Akbar called Birbal and asked him to draw a line on the floor. He asked Birbal to make that line smaller without erasing it. Birbal smiled and did it before Akbar could blink his eyes.

How did he managed to do it?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

You see a mathematical expression in the picture. Can you think of a movie that this expression refers to?