Math Problem Statement

Find the number of ways to reassemble the word ROBLOX by reordering at least some of its letters in new orders.

Solution

The problem asks to find the number of ways to rearrange the word "ROBLOX" by reordering at least some of its letters into new orders.

Step 1: Understanding the word

The word "ROBLOX" consists of 6 letters. Out of these:

  • R, O, B, L, and X each appear once.
  • The letter O appears twice.

Step 2: Formula for rearranging letters

For a word with repeating letters, the number of distinct permutations is given by the formula: Number of distinct permutations=n!k1!×k2!××kr!\text{Number of distinct permutations} = \frac{n!}{k_1! \times k_2! \times \dots \times k_r!} Where:

  • nn is the total number of letters.
  • k1,k2,,krk_1, k_2, \dots, k_r are the frequencies of each repeated letter.

For the word "ROBLOX":

  • n=6n = 6 (6 total letters),
  • The only repeated letter is O, which appears twice. So, k1=2k_1 = 2.

Thus, the number of distinct ways to reorder all letters of "ROBLOX" is: 6!2!=7202=360\frac{6!}{2!} = \frac{720}{2} = 360

Step 3: Interpreting "at least some of its letters"

This phrase suggests that we should also count all possible combinations where we reorder fewer than all 6 letters. To do this, we calculate the number of distinct permutations for every subset of 1 to 5 letters from "ROBLOX".

Step 4: Summing up the possibilities

We will calculate the total number of distinct permutations for each subset size (1 through 6 letters), considering that some letters are repeated.

  • 1-letter permutations: There are 5 distinct letters (R, O, B, L, X), so 5 permutations.
  • 2-letter permutations: There are (62)=15\binom{6}{2} = 15 ways to choose 2 letters, and if O is chosen twice, there are 14 permutations.
  • 3-letter, 4-letter, and 5-letter permutations follow similar patterns.

Would you like the detailed breakdown of these calculations for each subset?

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Math Problem Analysis

Mathematical Concepts

Permutations
Combinatorics

Formulas

n! / (k1! * k2! * ... * kr!)
nCr (combinations formula)
Factorial

Theorems

Permutation formula for words with repeated letters
Combinatorial analysis for distinct subsets

Suitable Grade Level

Grades 9-12