2026 EJC P2 Q7

A set of twins, Eugene and Eunice, is involved in a photoshoot with four other sets of twins.

1. Find the number of ways in which the ten people can be arranged in a row such that everyone is standing next to his or her twin.[2]
2. The ten people are now arranged in two rows, with 4 people in the front row and 6 people in the back row. Calculate the number of ways this can be done if Eugene and Eunice cannot be next to each other in the same row.[3]

The ten people are now seated at two round tables which can each seat five people. One table is black and the other is white.

3. Find the number of ways in which they can be seated such that no one is seated at the same table as his or her twin.[3]