What does this below rebus puzzle mean?

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

Can you solve the below algebraic mathematical equation?

(J+O+I+N+T)3 = JOINT

Yesterday I fell from 30 feet high ladder but I don't get hurt. Why?

The centre of the third figure is empty. What digit should fit inside?

Katniss and Peeta are liars. They both lie on some specific days.

Katniss lies on Fridays, Saturdays and Sundays. She speaks the truth on all other days.

Peeta lies on Tuesdays, Wednesdays and Thursdays. He speaks the truth on all other days.

Can you tell that one day of the week when both of them will say "Tomorrow, I will lie."?

If eleven plus two equals one, what does nine plus five equal?

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

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

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?