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04 Jun 2019, 01:45
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
71% (00:58) correct
29%
(01:17)
wrong
based on 528
sessions
History
Date
Time
Result
Not Attempted Yet
Count number of ways to arrange 4 people A, B, C, D in a row so that C, D not sit next to each other
A, 6
B. 12
C. 18
D. 24
E. 30
A, 6
B. 12
C. 18
D. 24
E. 30
04 Jun 2019, 01:50
Kudos
Bookmarks
number of ways to arrange 4 people A, B, C, D in a row=4!=24
number of ways to arrange 4 people A, B, C, D in a row, when C and D sit next to each other= 2*3!=12
number of ways to arrange 4 people A, B, C, D in a row, when C and D are not sitting next to each other= 24-12=12
number of ways to arrange 4 people A, B, C, D in a row, when C and D sit next to each other= 2*3!=12
number of ways to arrange 4 people A, B, C, D in a row, when C and D are not sitting next to each other= 24-12=12
Bunuel
04 Jun 2019, 01:56
Kudos
Bookmarks
First count without restriction:
4 people in a row, 4!=24 ways
now count the ways that are restricted:
CD as one person as they must seat to next each other and other two persons A and B, 3!=6
Note that CD order is different from DC, so multiply 6 by 2 and get 12
So total arrangements with restriction will be 24-12=12
IMO
Ans: B
4 people in a row, 4!=24 ways
now count the ways that are restricted:
CD as one person as they must seat to next each other and other two persons A and B, 3!=6
Note that CD order is different from DC, so multiply 6 by 2 and get 12
So total arrangements with restriction will be 24-12=12
IMO
Ans: B
