Question 146158
Use a combination. See http://www.mathagonyaunt.co.uk/STATISTICS/ESP/Perms_combs.html

15P6 =  15!/((15-6)!  * 6!) 
= (15*14*13*12*11*10)/ (6*5*4*3*2*1)
= (14*13*11*10)/4
= 7*13*11*5
= 5005