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Permutations and Combinations
Permutations, Grouping
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Grade 12
Question:
The number of ways in which 5 distinct books can be arranged on a shelf such that two specific books are always together is:
A. 24
B. 48
C. 120
D. 240
Step-by-Step Solution
Key Concept: Treat the two specific books as a single unit.
Step 1: Treat the two specific books as one unit. Total units = 4 (3 books + 1 unit). Step 2: Arrangements of 4 units = 4! = 24. Step 3: Internal arrangement of the two books = 2! = 2. Step 4: Total arrangements = 24 × 2 = 48.
Correct Answer:B
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