Math Problem Statement
A certain ice cream store has 31 flavours of ice cream available. In how many ways can we order a dozen cream cones if (i) we do not want the same flavour more than once? (ii) a flavour may be ordered as many as l2 times (iii) a flavour may be ordered no more than I I times.
Solution
Let's address each part of the problem one at a time.
(i) We do not want the same flavor more than once:
If we cannot repeat any flavor, the problem becomes choosing 12 distinct flavors out of 31 available. Since the order of the cones doesn't matter, it's a combination problem.
The number of ways is given by:
(ii) A flavor may be ordered as many as 12 times:
If there are no restrictions on how many times a flavor can be ordered, it means we can distribute 12 ice cream cones into 31 available flavors with repetition allowed. This is a classic "stars and bars" problem, where the formula is:
Here:
- (number of flavors)
- (number of cones)
So the total number of ways is:
(iii) A flavor may be ordered no more than 11 times:
This is a variation of the "stars and bars" problem with restrictions. The key is that no flavor can be selected more than 11 times.
To solve:
- First, calculate the unrestricted number of ways (as in part ii): .
- Subtract the cases where one flavor is chosen 12 times, leaving no cones for the other 30 flavors:
- If one flavor is chosen 12 times, the remaining 0 cones must be distributed among the 30 flavors. There is only 1 way to do this.
Thus:
Final Formulas:
- (i)
- (ii)
- (iii)
Let me know if you'd like the numerical evaluations for these!
Questions:
- Would you like detailed calculations of factorials for any of the parts?
- Are you familiar with the concept of "stars and bars" in combinatorics?
- Do you want the numerical solutions for these formulas?
- Would you like a breakdown of the restrictions in part (iii)?
- Are there any variations of this problem you'd like to explore?
Tip:
When solving combinatorics problems, always clearly identify if the order matters (permutations) or not (combinations) to use the right formula!
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Math Problem Analysis
Mathematical Concepts
Combinatorics
Permutations and Combinations
Stars and Bars Method
Formulas
Combination formula: C(n, k) = n! / (k! * (n-k)!)
Stars and Bars formula: C(n + k - 1, k)
Theorems
Fundamental Counting Principle
Suitable Grade Level
Grades 10-12
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