Q. If $\ ^{12}P_{r} = 1320$, then $r$ is equal to
A) 5
B) 4
C) 3
D) 2
Explanation
(c)
$\because\ \ {\ ^{12}P}_{r} = 1320 = 12 \times 11 \times 10$
$\Rightarrow \ \ \frac{12!}{(12 - r)!} = 12 \times 11 \times 10$
$\therefore\ \ \ r = 3$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.