Understanding \frac{10!}{5! \cdot 3! \cdot 2!: A Deep Dive into Its Value and Applications

Factorial expressions like \(\frac{10!}{5! \cdot 3! \cdot 2!}\ may seem complex at first, but they hold significant meaning in combinatorics, probability, and even algebra. In this SEO-optimized article, we’ll break down this expression, compute its value, explore its factorial roots, and uncover practical uses in real-world scenarios.


Understanding the Context

What is \(\frac{10!}{5! \cdot 3! \cdot 2!}\)?

The expression \(\frac{10!}{5! \cdot 3! \cdot 2!}\) is a ratio involving factorials, which are fundamental in mathematical computations—especially those related to permutations and combinations. Let’s unpack each component:

  • \(10! = 10 \ imes 9 \ imes 8 \ imes \dots \ imes 1 = 3,628,800\)
    - \(5! = 120\), \(3! = 6\), \(2! = 2\)

Substituting:

Key Insights

\[
\frac{10!}{5! \cdot 3! \cdot 2!} = \frac{3,628,800}{120 \cdot 6 \cdot 2} = \frac{3,628,800}{1,440} = 2,520
\]

So, \(\frac{10!}{5! \cdot 3! \cdot 2!} = 2,520\).


Why Factorials Matter: The Combinatorics Behind It

Factorials unlock powerful counting principles. The entire denominator—\(5! \cdot 3! \cdot 2!\)—typically appears in problems involving grouping, distribution, or partitioning. The numerator \(10!\) represents all possible arrangements of 10 distinct items. When divided by repeated groups (enforced by factorials in the denominator), this formula calculates a multinomial coefficient.

Final Thoughts

Specifically, \(\frac{10!}{5! \cdot 3! \cdot 2!}\) represents the number of distinct ways to divide 10 labeled objects into three labeled groups of sizes 5, 3, and 2, respectively. This kind of arrangement arises in:

  • Dividing tasks among teams with fixed sizes
    - Distributing items with indistinguishable elements in subsets
    - Calculating permutations of indistinct arrangements

Alternative Interpretations and Forms

This expression can be rewritten using multinomial coefficients:

\[
\frac{10!}{5! \cdot 3! \cdot 2!} = \binom{10}{5, 3, 2}
\]

Meaning “the number of ways to partition 10 objects into three groups of sizes 5, 3, and 2.”

Alternatively, it relates to:

  • Permutations with partitions: Arranging 10 elements with indistinguishable subsets
    - Statistics and probability: Calculating probabilities in grouped data samples
    - Algebraic identities: Expanding symmetric sums or generating functions in combinatorics