What does below chemistry rebus means?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

On her drawing table, Sayna lit 12 coloured candles. A few seconds later she blew two candles off.

How many candles Sayna have at the end?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

There is a box. The area of its top is 240 square units, the area of the front is 300 square units and the area of the end is 180 square units.

Can you calculate the dimensions of this box with the given data?

Can you count the number of squares in the figure below?

Who is that with a neck and no head, two arms and no hands? What is it?

What number when divided in half becomes zero?