probability that both modems selected are substandard

[Mary Jane]

A manufacturer stores computer modems in batches of 500. In one particular batch, 150 of the modems were substandard. An inspector selects 2 modems at random. What is the probability that both are substandard?

 

[pka]

\(\displaystyle \L \frac{150 \choose 2} {500 \choose 2}\)

 

[galactus]

Another way:

\(\displaystyle \L\\\left(\frac{150}{500}\right)\left(\frac{149}{499}\right)\)