Arrange and combine. The total number of incidents of any five pairs of seven different socks is C 14-5 (not easy to lose here) =14 *13 *12 *1*10/ Pairing logarithm of five socks is (C7-1) (C6-3) [(C2-1) 3] =1120. The probability that five socks have exactly one pair of matches =1120/2002 = 80/143.