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Odds and probability question

Ok so I am obviously no math wiz and don't know how this works but let's say you have 100 of somthing we will go with marbles here. OK so you have 100 marbles and 45 are red while 55 are (Duke) blue. Obviously you got a 45% chance of drawing a red if you pull only one out without looking, but if you place it back what are the odds you draw red again? How about drawing a red 5 times in a row if you put it back everytime?

"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge" -Stephen Hawking