20 passengers are to travelled by a doubled decked bus which can accommodate 13 in the upper deck and 7 in the lower deck. The number of ways that they can be distributed if 5 refuse to sit in the upper deck and 8 refuse to sit in the lower deck is:

(a) 25
(b) 21
(c) 18
(d) 15

• refused to sit on upperdeck --->5
  refused to sit on lowerdeck --->8
  total people remaining to arrange is = 20-13=7
  remaining place in upper deck = 5
  therefore, no. of ways possible= 7c5 = 21
  remaining place in lower deck = 2
  therefore, no. of ways possible= 7c2 = 21,also
  no. of ways possible is 21.
  
• 10 years agoHelpfull: Yes(40) No(3)
• people refused to sit on upperdeck=5
  " " " " " lowerdeck=8
  other people=7
  first place the 8 members on the upperdeck remaining(13-8=5 places on upperdeck)can be selected in 7c5 ways
  place the remaining people on lower deck(7)
  number of ways=7c5=21
  
• 10 years agoHelpfull: Yes(12) No(7)