Answer:
The least possible number is 13
Explanation:
Since there are 6 types of cars, 2 kinds of radios and 5 types of Tv, then, there are a total of 6*2*5 = 60 combinations.
Each family should have a Tv, can and radio matching one of this 60 combinations, and the best way to ensure that the number of families that have the same kind of car, radio and tv is the least as possible, we are better sharing each combination in equal parts, or at least almost equal.
Since there are 780 families and a total of 780 combinations, then, each combination should be used by a total of 780/60 0 13 families.