probability of roads from A-B at least 5 miles = 2/3
probability of roads from A-B NOT at least 5 miles = 1- 2/3 = 1/3
probability of roads from B-C at least 5 miles = 1/4
probability of roads from B-C NOT at least 5 miles = 1- 1/4 = 3/4
There are 3 cases - at least 1 road selected should be at least 5 miles long
CASE 1=probability of selecting road 5 miles long A-B * probability of NOT selecting road 5 miles long B-C
2/3 * 3/4 = 6/12
CASE 2=probability of NOT selecting road 5 miles long A-B * probability of selecting road 5 miles long B-C
1/3 * 1/4 = 1/12
CASE 3=probability of selecting road 5 miles long A-B * probability of selecting road 5 miles long B-C
2/3 * 1/4 = 2/12
Total probability = 6/12 + 1/12 + 2/12 = 9/12 = 3/4
No rest for the Wicked....