6 boys B1, B2, B3, B4, B5 and B6 are sitting around a rectangular table facing towards the centre (not necessarily in the same order). Two boys are sitting on each longer side and one boy is sitting on each shorter side of the table. B1 sits second to the left of B6. B4 sits second to the left of B5. B5 is the immediate neighbour of B6 and B2. B5 is not sitting opposite to B4. B1 is not sitting on a shorter side.

Which pair of boys is sitting on a shorter side of the rectangular table?

B1 is not sitting on a shorter side. B1 sits second to the left of B6.

Here B1 is possible in two places which are given below in Case(i) and Case(ii).

B5 is the immediate neighbour of B6 and B2.

 B4 sits second to the left of B5.

B5 is not sitting opposite to B4.

In Case(i), the above given condition is not applicable. So this case is eliminated.

 Now only B3 is remaining which can be placed in the blank space.

According to the above arrangement, B2 and B4 are sitting on a shorter side of the rectangular table.