A shop has 4 distinct flavors of ice-cream. One can purchase any number of…
2025
A shop has 4 distinct flavors of ice-cream. One can purchase any number of scoops of any flavor. The order in which the scoops are purchased is inconsequential. If one wants to purchase 3 scoops of ice-cream, in how many ways can one make that purchase?
- A.
4
- B.
20
- C.
24
- D.
48
Attempted by 82 students.
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Correct answer: B
Answer: 20
Explanation: We need the number of ways to choose 3 scoops from 4 distinct flavors when repetition is allowed and order does not matter. This is the number of multisets of size 3 from 4 types.
Use the combinations with repetition formula (stars and bars): the number is C(n + k - 1, k), where n = number of flavors and k = number of scoops.
Here n = 4 and k = 3, so the count is C(4 + 3 - 1, 3) = C(6, 3).
Compute C(6,3) = 6*5*4 / (3*2*1) = 120 / 6 = 20.
Quick notes on the incorrect numerical choices:
The value 4 counts only the cases where all three scoops are the same flavor (one per flavor).
The value 24 is 4P3, counting ordered selections of three distinct flavors with no repetition; that assumes order matters and repeats are forbidden, which does not match the problem.
The value 48 does not follow from the correct model and likely comes from mixing different incorrect assumptions about order and repetition.
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