If 6Pr = 360 and If 6Cr = 15, find r ?	Choose the most appropriate option:
A) 5	B) 6	C) 4	D) 3	E) 2
Solution:   nPr = nCr�r!   6Pr = 15 *r!   360 =15 *r!   r! =360 /15= 
<gadget id="calculator">360 /15</gadget>
<output>24</output>
24   r!= 4*3*2*1   =&gt; r! =4!   Therefore, r = 4.   Answer: Option 4
<result>C</result>
If 6Pr = 360 and If 6Cr = 15, find r ?