What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

The host of a game show offers the guest a choice of three doors. Behind one is an expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

What do you think with the below Picture ?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

The following sentence is false. The preceding sentence is true.
Are these two sentences true or false?

What do you answer even though it never asks you questions?

I have feet, but no legs. Which animal Am I?

What is at the end of a rainbow?

Before Balboa discovered the Pacific Ocean, which was the largest ocean before that?

who is silent in the parliament?