The Art of the Fruit Basket
A Combinatorial Journey
Imagine you are standing in front of a bountiful basket containing 8 oranges, 7 red apples, and 5 white apples. Your task is to select exactly 5 fruits subject to specific constraints: at least 2 oranges, at least 1 red apple, and at least 1 white apple.
This is a puzzle of constraints. Let us break it down systematically.
Analyzing the Setup
We are selecting a total of n=5 fruits. Let O be the number of oranges, R be the number of red apples, and W be the number of white apples.
Our constraints are defined as:
O≥2, R≥1, and W≥1.
Given the total sum O+R+W=5, we identify the possible integer combinations that satisfy these inequalities. Starting with the minimum requirements (2+1+1=4), we have exactly 1 fruit remaining to distribute.
This leads to three distinct, mutually exclusive cases:
1. Case 1: (O=2,R=1,W=2)
2. Case 2: (O=2,R=2,W=1)
3. Case 3: (O=3,R=1,W=1)
The Three Paths
We calculate the number of ways for each path using the combination formula:
nCr=r!(n−r)!n!
For Case 1 (2 Oranges, 1 Red Apple, 2 White Apples):
The number of ways is calculated as:
8C2×7C1×5C2=28×7×10=1960
For Case 2 (2 Oranges, 2 Red Apples, 1 White Apple):
The number of ways is calculated as:
8C2×7C2×5C1=28×21×5=2940
For Case 3 (3 Oranges, 1 Red Apple, 1 White Apple):
The number of ways is calculated as:
8C3×7C1×5C1=56×7×5=1960
Final Calculation
To find the total number of ways to select the fruits, we sum the results of the three mutually exclusive cases:
Total Ways=1960+2940+1960
By breaking the complex constraints into simple, manageable cases, we have determined that there are exactly 6860 ways to select the fruits.