Difficulty: Medium
Correct Answer: 120,960
Explanation:
Problem restatement
Arrange the 11 letters of 'MATHEMATICS' so that all vowels remain in one block.
Given data
Concept/Approach
Treat the 4 vowels as one super-block. Then arrange this block with the 7 consonants around it, accounting for repeated consonants. Multiply by the internal arrangements of the vowels (accounting for repeated A).
Step-by-Step calculation
Consonants: M, M, T, T, H, C, S (7 items with repeats M(2), T(2))Entities to arrange = 7 consonants + 1 vowel-block = 8Ways to arrange these 8 = 8! ÷ (2! 2!) = 40320 ÷ 4 = 10080Vowel-block arrangements (A, A, E, I) = 4! ÷ 2! = 12Total arrangements = 10080 × 12 = 120,960
Verification/Alternative
Check counts of repeats carefully: two M's and two T's in the outer arrangement; two A's inside the block.
Common pitfalls
Ignoring duplicate letters (overcounting), or forgetting to multiply by internal arrangements of the vowel-block.
Final Answer
120,960
Discussion & Comments