A letter has been put in either File A or File B or File C. The percentage of letters addressed to an overseas destination is 5% for File A, 10% for File B and 15% for File C. The probability that a letter has been put in File A is 60%, File B 30% and File C is 10%. If a letter is drawn at random is addressed to an overseas destination, what is the probability that it was put in File A? File B? File C?
Here's what I did. I made a table, below:
so, A = 0.4, B = 0.4, C = 0.2? Can somebody confirm I'm on the right track?
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Edited by stapel -- Reason for edit: adding "code" tags
Here's what I did. I made a table, below:
Code:
File Overseas % Prob = Cond Prob Cond Prob/Total Cond Prob
A 0.05 0.6 0.03 0.03 /0.75 = 0.40
B 0.10 0.3 0.03 0.03 /0.75 = 0.40
C 0.15 0.1 0.015 0.015/0.75 = 0.20______________________________
Edited by stapel -- Reason for edit: adding "code" tags