To have the smallest number of hotdogs and hotdog buns, we have to find the least common multiple of 6 and 10. The LCM is the smallest number that is a multiple of both 6 and 10.
To find the LCM, we can list the multiples of each number until we find the first multiple that they have in common:
Multiples of 6: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60 and ongoing.
Multiples of 10: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 and ongoing.
The first multiple that they have in common is 30, so the LCM of 6 and 10 is 30.
Since hotdogs come in packs of 6 and buns come in packs of 10, we need to make sure that the number of hotdogs we cook is a multiple of 6 and the number of buns we buy is a multiple of 10. Therefore, we need to cook 30 hotdogs so that we can buy 3 packs of hotdogs (18 hotdogs) and 3 packs of buns (30 buns).
Therefore, Cher should cook 30 hotdogs to have the smallest number of hotdogs and hotdog buns.