In a school, 280 students studied chemistry, 254 students studied physics and 280 students studied biology.

97 students studied chemistry as well as physics, 138 students studied physics as well as biology and 152 students studied chemistry as well as biology.

73 students studied all the three branches.

Can you find out the total number of students?

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

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

What will you call your mother's brother's brother-in-law?

It is always ahead of me yet I can never see it. What is it?

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

I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but water kills me. What am I?

You can see it everyday, But cannot touch it at will. What is it?

I am the first thing you need while camping.
I am always with the person named Marcos Valencia and Carrick.
But Pogba Zlatan and Rooney think I am wasteful and do not need me.
I am the second to the last thing to add when you are making a patch.

What am I?