Can you place six X (crosses) in below board without making three in a row in any way ?

Can you replace the question mark with the correct number?

Which is faster, Heat or Cold ? Explain.

I get hot but I never sweat,
I cook food but I am not a chef,
I have a door but you can't enter me,
I have a light but I am not a lamp.
Who am I?

What breaks yet never falls, and what falls yet never breaks?

What's the best place to go shopping in the ocean?

Find the value of "?" in the ball picture Riddle below:

What kind of band never plays music?

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

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different. How do you measure 45 minutes?