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# If $^n P_r=30240$ and $^n C_r=252$ then the ordered pair (n,r)=

$\begin {array} {1 1} (1)\;(12,6) & \quad (2)\;(10,5) \\ (3)\;(9,4) & \quad (4)\;(16,7) \end {array}$
Can you answer this question?

(2) (10,5)
answered Nov 7, 2013 by