Problema Solution
Al,Barb,Cy,Di,Ed,Fred,and Greg stand in a straight line. If Al must stand next to Barb and Cy must stand next to Di, in how many ways can these seven people line up?
Answer provided by our tutors
Some possible ways are:
AB, CD, E, F, G
BA, CD, E, F, G
BA, DC, E, F, G
AB, DC, E, F, G
Notice that the order of E, F and G is the same while A and B, and C and D are altering.
Thus the total number of ways is:
4*5! = 5*1*2*3*4*5 = 5*120 = 600 ways.