# Working with conditional probability.

There are 12 light bulbs, 5 of which are defective. All bulbs look alike and have an equal probability of being chosen. Three light bulbs are selected and placed on the table.

Find the probability that:

a) All three are defective.

b) Two are defective.

c) That none are defective.

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#### Solution Preview

Assuming no replacement

Let defective bulbs be D

non defective bulbs be ND

a) P(all 3 defective) = D x D x D

= ...

#### Solution Summary

The probability of picking defective light bulbs is calculated.

$2.19