If 42(<sup>n</sup>P<sub>2</sub>) = <sup>n</sup>P<sub>4</sub> then the value of n is
\({}^nP_4 = n(n-1)(n-2)(n-3)\) and \({}^nP_2 = n(n-1)\).
\(42 \cdot n(n-1) = n(n-1)(n-2)(n-3) \Rightarrow (n-2)(n-3) = 42 = 7 \times 6\)
So \(n - 2 = 7\), and \(n = 9\).
Answer: (C) 9
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