Wednesday, May 1, 2013

Tiles in a bag

a bag containing 9 blue tiles 6 green tiles 5 red tiles what is the probability of drawing a red tile followed by a blue tile if the first tile is not returned to the bag?


Solution:


9 blue, 6 green, 5 red means total of 20 tiles 

P%28red%29=5%2F20 

Now only 19 tiles remain, but all blue tiles since we are looking at the situation where 
the first was red... 
P%28blue%29=9%2F19 

The probability of both events happening as described is their product: 

P%28red+then+blue%29=%285%2F20%29%289%2F19%29=9%2F76

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