JAMB - Mathematics (1992 - No. 43)
Five people are to be arranged in a row for a group photograph. How many arrangements are there if a married couple in the group insist on sitting next to each other?
48
24
20
10
स्पष्टीकरण
Treat the couple as one block, giving us 4 units to arrange (the couple + 3 others).
Arrange the 4 units: 4! = 4 x 3 x 2 x 1 = 24.
Arrange the couple within their block: 2! = 2 x 1 = 2.
Total arrangements: 4! × 2! = 24 × 2 = 24 × 2 = 48.
Thus, the total number of arrangements is 48.