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A shipment containing fair and defective alarm clocks
Problem 1
A shipment at a department store contains 40 alarm clocks. 4 of them are defective.
If 6 alarm clocks are removed from the shipment at random, find the probability that four of them are defective.
Solution
First find in how many ways 6 alarm clocks can be taken from the entire set of 40 alarm clocks.
This number is = = 3,838,380.
Next, find in how many ways 2 alarm clocks can be selected from the remaining 40-4 = 36 to get 6 alarm clock,
assuming that 4 defective alarm clock are just removed from the total set of 40.
This number is = = 630.
Now the probability under the question is = 0.000164.
Answer. 0.000164.
