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One box contains 30 purple balls and 20 red balls, another

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New post 08 Nov 2006, 15:39
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One box contains 30 purple balls and 20 red balls, another box contains 15 purple balls and 35 red balls, if Wendy randomly chooses one box and draws one ball from it, what will be the possibility that the ball will be purple?
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New post 08 Nov 2006, 16:19
Prob fo selecting 1st box = 1/2 and prob to find puple in that 30/50
(1/2)*(3/5)=3/10
prob for slecting 2nd box 1/2 and prob to find purple 15/50

(1/2)*(15/50)= 3/20

combined 3/10+3/20=9/20
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New post 08 Nov 2006, 17:10
Outcome can be purple from box1 OR purple from 2

Probability of picking eithe box = 1/2
Probability of picking purple from box1 = 30/50 * 1/2 = 3/10
Probability of picking purple form box2 = 15/50 * 1/2 = 3/20

Total = 3/10 + 3/20 = 9/20

(Easily understood if you drew a probability tree)
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New post 08 Nov 2006, 20:18
9/20.......calculations as explained by other friends
  [#permalink] 08 Nov 2006, 20:18
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One box contains 30 purple balls and 20 red balls, another

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