Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

What does below chemistry rebus means?

With the help clues provided in the image, can you find the 5 digit key?

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

You’re out on the water and see a boat filled with people. You look away for a second and look back again, but this time you don’t see a single person on the boat. Why? Hint: The boat did not sink.

By using 'because' continuously three times, can you make an English statement ?

Why Wine Glass Stem is so long?

People put me on the table and cut me but do not eat me. What am I?

Three brothers Jacob, John, and James live in Mexico City. The product of the ages of these brothers is 175. Jacob and John are twins. How old is James?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?