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1. If 6Pr = 360 and If 6Cr = 15, find r ?
6Pr = 15 × r!
360 = 15 × r!
r! = = 24
r! = 4 × 3 × 2 × 1
⇒ r! = 4!
Therefore, r = 4
Solution:
nPr = nCr × r!6Pr = 15 × r!
360 = 15 × r!
r! = = 24
r! = 4 × 3 × 2 × 1
⇒ r! = 4!
Therefore, r = 4