12towns are divided into 4group of 3 in each.if any two towns in same group are connected by 3 direct lines and by different group by 1 direct line.find the total no of direct line?

• 1st group-towns a,b,c
  3 lines between 2 towns a,b
  so 3*3 lines as a,b ,, a,c ,, b,c
  so 9 lines in a group
  9*4=(36) lines all 4 groups..
  now 9 lines from a to all towns of other grps..
  similarly 9+9 for b and c
  total (27)
  6*3=(18) for 2nd grp
  3*3=(9) for 3rd grp
  36+27+18+9 = 90 answer
• 10 years agoHelpfull: Yes(25) No(0)
• sorry,ans will be 90
• 10 years agoHelpfull: Yes(7) No(2)
• 2 towns are connected via 3 lines so 3 towns in a group will be connected using 6 lines (i.e. A to B and B to C and 3 for each)
  so there are 4 groups , so 4 X 6 = 24 lines are required to connect each towns in a group.
  Now to connect towns of 4 groups, 3 line will be reuired.
  Total no of direct lines = 24 + 3 = 27...
• 10 years agoHelpfull: Yes(3) No(3)
• ans is 144
  
• 10 years agoHelpfull: Yes(2) No(3)
• 2 towns are connected via 3 lines so 3 towns in a group will be connected using 9 lines (i.e. A to B and B to C and A to C)
  so there are 4 groups , so 4 X 9 = 36 lines are required to connect each towns in a group.
  Now to connect towns of 4 groups, 4 line will be required.
  Total no of direct lines = 36 + 4 = 40...
• 10 years agoHelpfull: Yes(1) No(1)
• i think 144
• 10 years agoHelpfull: Yes(0) No(6)
• one town has the total direct line ARE 3*3*3=27 SIMILARLY THE 2 LINE HAVE 27 DIRECT LINES.
  TOTAL DIRECT LINE CONNECTED=27+27=54
  EVERY GROUP HAVE 3 TOWN SO TOTAL NUMBER OF WAY to DIRECT LINE= 3!*54=324
  
• 10 years agoHelpfull: Yes(0) No(2)
• 3*3=9*3=36
  9c2=36
  36+36=72
  so,72 is ans
• 10 years agoHelpfull: Yes(0) No(1)