# picking 2 defective question I cant understand answer

• March 17th 2011, 11:29 AM
angypangy
picking 2 defective question I cant understand answer
Hello

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

I calculated 6/100 * 6/100 = 9/2500 but the correct answer is 1/330. how do you arrive at 1/330?

Angus
• March 17th 2011, 11:38 AM
Plato
Quote:

Originally Posted by angypangy
In a shipment of 100 televisions, 6 are defective. If a person buys two televisions from that shipment, what is the probability that both are defective?
I calculated 6/100 * 6/100 = 9/2500 but the correct answer is 1/330. how do you arrive at 1/330?

It should be $\frac{6}{100}\frac{5}{99}$
• March 18th 2011, 09:38 AM
angypangy
Ah of course. Thanks. I was forgetting that it would be conditional prob.