3x Math Riddle's, #1

Question: If wanted, use paper!, You may only put 1 line on a number!, how?, thats up to you: 5 + 45 = 450?!.. 883 x 2 = 1776?!.. 282 - 6 x 0 = 288?!..

Question: When is 99 more than 100?

Question: There is a 5 gallon and a 3 gallon box. You also have a hose with unlimited water. How are you gonna make the 5 gallon have 4 gallons using your items? (You do not know the exact measure measurements of a gallon)

Question: In a house of Kardak's family each brother have a sisters as double as their brothers and each sister have brothers as same as their sister. How many brothers and sisters in Kardak's family ?

Question: How can you make the following true by adding a single line: .9 = 1.

Note: ≠ is not the answer.

Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?

The glass is a right cylinder.