A drawer contains 200 distinct pairs of socks, and three socks are chosen at random. The probability that the three socks contain a pair of socks.

hi vivek

when u select a pir out of 400 socks then the remaining will be 398

so no. of favourable cases will be  200 * 398

IF THERE ARE 200 PAIRS OF SOCKS THEN THERE WOULD BE 200 WAYS TO SELECT A PAIR 

AND THE THIRD SOCK WILL BE ONE OF THE REMAING 400 SO THE 

NUMBER OF FAVOURABLE CASES IS 200 * 400 

AND THE SAMPLE SPACE WILL BE SELECTING ANY 3 OUT OF 400 

SO C(400 , 3) 

SO PROBABILITY IS (200* 400)/ C (400 , 3)