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Probability Questions


Lasha

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Hi everybody! Can anybody solve this probability question?

 

In a shipment of 100 televisions, 6 are defective. If a person buys two televisions, what is the probability that both are defective?

 

A)3/100 B) 9/2500 C)1/330 D)None of the above

I think the answer is B but the answer key says it's C.

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In a shipment of 100 televisions, 6 are defective. If a person buys two televisions, what is the probability that both are defective?

 

A)3/100 B) 9/2500 C)1/330 D)None of the above

I think the answer is B but the answer key says it's C.

 

Hi Lasha :D

I think the answer should be C.

Here is my solution.

 

The probability that the first TV is defective is 6/100 or 3/50. Right?

However, the probability that the second TV is defective is 5/99. Why? It's because now there are only 5 defective TVs left in the pool of 99 TVs.

 

Ultimately, the final solution is 6/100*5/99 which is 1/330.

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I don't known about GRE, but I don't think it is a GMAT question. Moreover, the question itself is unclear. It only says out of a 100 TV, 6 is defective. It gives you the average chance of getting a defective TV of 0.06. It doesn't tell you that both TV in deed come from the same shipment. They could, in fact, come from different shipment. Therefore, having the same probability of 0.06 each in getting a bad TV. Under this assumption, the correct answer is B instead of C.

 

 

Long long

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  • 4 years later...

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