Five people of A,B,C,D,E stand in one line of side.
How many ways of forming line in case A and B should be side-by-side are there?
Answer
48 ways
Solution
Since A and B should be side-by-side, assume A and B with one in a mass.
Then the number of ways of four people AB, C, D, E stand is 4 × 3 × 2 × 1 = 24 ways.
The number of ways of the row of A and B is 2 ways which are AB and BA.
Therefore the ways of forming line are 24 × 2 = 48 ways in total.
