Given: cards 1,2,3,4,5,6 → envelopes 1,2,3,4,5,6 (one each)
no card i in envelope i
1→envelope 2(fixed)
To find: number of such arrangements
1. fix card 1→envelope 2
2. arrange the remaining 5 cards avoiding their own envelopes
3. count with inclusion-exclusion
cards left: {2,3,4,5,6}
envelopes left: {1,3,4,5,6}
without restriction: 5!=120
forbidden: card i→envelope i,i=3,4,5,6
4 forbidden events
N=5!−(14)4!+(24)3!−(34)2!+(44)1!
5!=120
(14)4!=4×24=96
(24)3!=6×6=36
(34)2!=4×2=8
(44)1!=1
N=120−96+36−8+1
=24+36−8+1=53
!6=265,5265=53 ✓
53⇒option (3)