其它
Two different numbers are randomly selected from the set $-5, -3, -1, 3, 5$~and multiplied together. What is the probability that the product is a negative number? (adapted from $2016$ AMC $8$ Problem, Question \#$13$) 
Overseas Competition->Knowledge Point->Counting Modules->Statistics and Probability
$\frac25\times\frac34+\frac35\times\frac24=\frac{3}{5}$ 