In a group of boys the number of arrangement of 4 boys is 12 times the number of arrangements of 2 boys. The number of boys in the group is
  • a)
    10
  • b)
    8
  • c)
    6
  • d)
    none of these
Correct answer is option 'C'. Can you explain this answer?

CA Foundation Question

2 Answers
Dinesh Kukreja answered Aug 22, 2018
 Assume that there are n boys.
nP4=12*nP2
n!/(n-4)!=12*n!/(n-2)!
(n-2)!/(n-4)!=12
(n-3)(n-4)=12
n^2-5n-6=0
(n-6)(n+1)=0
n=6

Sahirah answered Sep 18, 2020
4boys;12times::2boys;X time
so, 12*2/4=6times

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