How many ways of forming line that four children stand in one line of side among parents are there?
Parents stand at the both ends of the line.
Answer
48 ways
Solution
The way of forming line of four children is 4 × 3 × 2 × 1 = 24 ways.
The way of forming both ends of parents is two ways of father-mother, mother-father.
Therefore, 24 × 2 = 48 ways in all.
