To find the experimental probability of at least 2 out of 5 flights arriving late, we need to count the number of times the digits 7, 8, or 9 appear in each group of 5 digits, and see how many of those groups have 2 or more of those digits. We can organize our counts in a table like this:
| | Flights | with | Late | Arrivals | |
|---|--------|-----|---------|-------------|
| | Digit | 7 | Digit | 8 | Digit | 9 | Total |
| 1 | 0 | 0 | 0 | 0 | 1 | 1 |
| 2 | 2 | 0 | 0 | 0 | 3 | 3 |
| 3 | 0 | 1 | 1 | 1 | 0 | 3 |
| 4 | 0 | 0 | 1 | 2 | 1 | 4 |
| 5 | 0 | 0 | 0 | 2 | 3 | 5 |
| 6 | 0 | 0 | 2 | 1 | 2 | 5 |
| 7 | 0 | 1 | 0 | 2 | 2 | 5 |
| 8 | 0 | 0 | 2 | 0 | 3 | 5 |
| 9 | 0 | 2 | 0 | 1 | 2 | 5 |
| 10 | 0 | 1 | 1 | 0 | 3 | 5 |
| 11 | 1 | 0 | 1 | 0 | 3 | 4 |
| 12 | 1 | 0 | 0 | 2 | 2 | 5 |
| 13 | 0 | 0 | 3 | 0 | 2 | 5 |
| 14 | 1 | 1 | 0 | 1 | 2 | 4 |
| 15 | 1 | 0 | 0 | 3 | 1 | 4 |
| Total | 5 | 6 | 11 | 15 | 28 | 60 |
For example, in row 2, we see that there are 3 groups of 5 digits where there are at least 2 late arrivals (digits 7, 8, or 9). To find the experimental probability, we need to add up the total number of groups that meet the criterion (at least 2 late arrivals) and divide by the total number of groups:
Experimental probability = (number of groups with at least 2 late arrivals) / (total number of groups)
Experimental probability = (11 + 15 + 28) / 60
Experimental probability = 54/60
Experimental probability = 9/10
Therefore, the answer is (C) start fraction 9 over 20 end fraction.