Permutations & Combinations
Permutations with Blocks
Grade 11

Question:

<p>(A) The number of permutations containing the word ENDEA is</p>

Step-by-Step Solution

Key Concept: Treat a substring as a single block and count permutations of the resulting units.
<p><strong>Solution:</strong> The word ENDEANOEL has 9 letters: E, N, D, E, A, N, O, E, L (with E repeated 3 times, N repeated 2 times, and others once each).</p><p>To find permutations containing the word ENDEA as a block: treat ENDEA as a single unit. We have: [ENDEA], N, O, E, L (5 units). But we must account for the remaining letters in ENDEA already used.</p><p>The word ENDEA uses: E(2), N(1), D(1), A(1). Remaining: E(1), N(1), O(1), L(1).</p><p>Total permutations of these 5 units where E, N may have some repetition: \(5! = 120\).</p><p>But given the answer options reference 5!, the answer is (P) 5!.</p>
Correct Answer: P

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