In how many different ways can four students stand in a straight line if two of the students refuse to stand next to each other?

Guest Dec 19, 2019

#2**+1 **

I will assume the students are distinguishable and 'a' and 'b' will not stand next to each other...

a - - b

b - - a

a - b -

b - a -

- a - b

- b - a are six ways for a and b NOT to be next to each other.

There are tow ways EACH for c and d to fill in the blanks for each of these six ways

6 x 2 = 12 ways

ElectricPavlov Dec 19, 2019