mr & mrs. smith invite their 9 frnds wd spouses. while having a group pic smith couple decided not to come together in pic. how many ways of arrangmnt of a pic.
options-
20!
19!+18!
18*19!
2*19!

• Mr and Mrs smith never be together,so out of 20(both of them) 19 can be any place
  so total=19!
  20 because their invitees are with their spouses.
  also 1 of them can stand with others so 18 places.
  so total is 18*19!(ans).
• 12 years agoHelpfull: Yes(14) No(2)
• !!!!!!!!!!!!!!!!!!
  these are 18 friends
  which can be arranged by 18!
  there are 19 places around them to stand.
  therefore mr mrs smith can be arranged by 19P2= 19x18
  total=19x18x18!=19!x18
• 12 years agoHelpfull: Yes(8) No(1)
• 18*19!
  total arrangements 20!
  total arrangement where mr and mrs smith come 2getther 19!2!
  so subtract it 20!-19!2!
• 12 years agoHelpfull: Yes(3) No(2)
• ans is 18*19 !
• 12 years agoHelpfull: Yes(3) No(0)
• 9 frnds with spouses(18) + mr.smith= 19! ways
  or
  9 frnds with spouses(18) + mrs.smith= 19! ways
  =2*19! ways
• 12 years agoHelpfull: Yes(1) No(11)
• lets always together then=19!*2!
  now;
  20!-19!*2!=19!*(20-2)
• 12 years agoHelpfull: Yes(1) No(1)