SOLUTION: 37. A box is filled with 12 locks of which 4 are defective. All the locks look alike and have equal probability of
being defective. 3 locks are chosen and placed in a box. What is
Algebra.Com
Question 875430: 37. A box is filled with 12 locks of which 4 are defective. All the locks look alike and have equal probability of
being defective. 3 locks are chosen and placed in a box. What is the probability that 2 locks are defective?
Found 2 solutions by jim_thompson5910, bond:
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
There are 12 C 3 = 220 ways to pick 3 locks from the pool of 12.
-------------------------------------------------------
There are 4 defective locks.
There are 12-4 = 8 non-defective locks.
There are (4 C 2)*(8 C 1) = (6)*(8) = 48 ways to pick 3 locks where 2 are defective and 1 is non-defective.
-------------------------------------------------------
Probability: (# of ways to pick 3 locks with 2 defective)/(# of ways total) = 48/220 = 12/55
Answer by bond(4) (Show Source): You can put this solution on YOUR website!
The probability of 2 defective among 3 chosen is = 4/12 * 3/11 * 8/10
This can done in 3 ways hence = 3 * 4/12 * 3/11 * 8/10 = 12 /55.
RELATED QUESTIONS
A box contains 12 light bulbs of which 5 are defective. All the bulbs look alike and have (answered by ikleyn)
You have a box of chocolates that contains 51 pieces of which 29 are solid chocolate, 12... (answered by greenestamps)
In a shipment of 50 transformers, 10 are known to be defective. If 30 transformers are... (answered by Edwin McCravy)
In a shipment of 50 transformers, 7 are known to be defective. If 30 transformers are... (answered by stanbon)
Allison has 6 keys and 4 locks. Each lock can be locked by only one of the 6 keys, and... (answered by ikleyn,greenestamps)
You have a box of chocolates that contains 55 pieces of which 32 are solid chocolate, 16... (answered by ikleyn)
You have a box of chocolates that contains 20 pieces of which:
5 are solid chocolate,
8 (answered by ikleyn)
A box contains 10 items, of which 3 are defective and 7 are non-defective. Two items are... (answered by uday_ra)
The combination locks on the lockers at Hillside School have numbers from 0 through 39... (answered by math_helper)