Single correct option
What is the largest integer n such that 12ⁿ divides 50! (50 factorial)?
- A. 16
- B. 22
- C. 23
- D. 24
Show answer and solution
Answer: (B) 22
12ⁿ = 2²ⁿ × 3ⁿ, so we need enough 2s and enough 3s in 50!.
Powers of 2 in 50!: 25 + 12 + 6 + 3 + 1 = 47 ⇒ at most ⌊47/2⌋ = 23 twelves.
Powers of 3 in 50!: 16 + 5 + 1 = 22 ⇒ at most 22 twelves.
The scarcer resource decides: n = 22.
Trap: 23 comes from checking only the 2s; 16 counts only multiples of 3 once.
Powers of 2 in 50!: 25 + 12 + 6 + 3 + 1 = 47 ⇒ at most ⌊47/2⌋ = 23 twelves.
Powers of 3 in 50!: 16 + 5 + 1 = 22 ⇒ at most 22 twelves.
The scarcer resource decides: n = 22.
Trap: 23 comes from checking only the 2s; 16 counts only multiples of 3 once.
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