Two distinct numbers are selected simultaneously and at random

20 possible selections

1 will divide into 5 selections

2 will divide into 2 selections (4 and 6)

3 will divide into 1 selection (6)

 

so   8 out of 20     8/20 = 2/5

6 C 2 =15 combinations as follows:

 

{1, 2} | {1, 3} | {1, 4} | {1, 5} | {1, 6} | {2, 3} | {2, 4} | {2, 5} | {2, 6} | {3, 4} | {3, 5} | {3, 6} | {4, 5} | {4, 6} | {5, 6} (total: 15)

 

Probability = 8 / 15