# Among the 16 bulbs, 3 are non-standard. Find the probability that two bulbs taken at the same time turn out to be non-standard

August 3, 2020 | Education

| Let’s designate events:

A – “the first bulb will be non-standard”;

B – “the second bulb will be non-standard”.

Events A and B are dependent.

The probability that the first bulb is non-standard:

P = 3/16

The probability of the second light bulb being non-standard, provided that the first light bulb turned out to be non-standard, is

P = 2/15

It is taken into account that the total number of bulbs and the number of non-standard among them will decrease by one if the first light bulb is non-standard. According to the theorem of multiplication of probabilities for two dependent events

P = 3/16 * 2 * 15 = 1/40 = 0.025

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