There are six teachers. Out of them two are primary teachers and two are secondary teachers. They are to stand in a row, so as the primary teachers, middle teachers and secondary teachers are always in a set . The number of ways in which they can do so, is-

Correct Answer: 48
There are 2 primary teachers.
They can stand in a row in
P (2, 2) = 2! = 2 × 1 ways = 2 ways
∴ Two middle teachers.
They can stand in a row in
P (2, 2) = 2! = 2 × 1 ways = 2 ways
There are two secondary teachers.
They can stand in a row in
P (2, 2) = 2!= 2 × 1 ways = 2 ways
These three sets can be arranged themselves in
3! ways = 3 × 2 × 1 = 6 ways
Hence,, the required number of ways
= 2 × 2 × 2 × 6
= 48 ways