SOLUTION: a box contain 50 light bulbs, of which 4 are detective. you purchase two bulbs from this box. what is the probability that both will be defective?

Question 1011009: a box contain 50 light bulbs, of which 4 are detective. you purchase two bulbs from this box. what is the probability that both will be defective?
Answer by mathmate(429) (Show Source): You can put this solution on YOUR website!

Question:
a box contain 50 light bulbs, of which 4 are detective. you purchase two bulbs from this box. what is the probability that both will be defective?

Solution:
Given 4 out of 50 light bulbs are defective.
Draw two from the batch.
Let D=event that light bulb drawn is defective.
and ~D=event that light bulb drawn is normal.

Need to find P(DD)
Recall that there are 4 defectives out of 50 at the first draw, and 3 defectives out of 49 at the second draw.
Using the multiplication rule, then

Answer: the probability of drawing two defective light-bulbs is 6/1225
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