] = 44 Note that if r (0 ≤ r ≤ n) objects occupy the original places and none of the remaining (n - r) objects occupies its original places then the number of such arrangements =
n
Cr(n−r)![1−
1
1!
+
1
2!
−
1
3!
+ ... + (−1)n−2
1
(n−r)!
]
or 5 letters 5 directed envelopeAll the of letters Put wrong wrong : Number of ways = =[1−