Let's break down the given conditions step by step to determine the seating arrangement of the 8 persons around the circular table.
- Both P and R are adjacent to Q: This means Q is sitting exactly between P and R. The sequence is either P−Q−R or R−Q−P.
- Both T and R are adjacent to S: This means S is sitting exactly between T and R. The sequence is either T−S−R or R−S−T.
Combining the first two conditions, since R is common to both, the 5 persons must sit together in a contiguous block. The sequence of these 5 persons is either P−Q−R−S−T or T−S−R−Q−P.
- Both U and W are adjacent to V: This means V is sitting exactly between U and W. The sequence is U−V−W or W−V−U. This forms a block of 3 persons.
Since there are 8 seats in total, these two blocks (one of 5 persons and one of 3 persons) will complete the circle.
- S and W are on opposite chairs: In a circular arrangement of 8 seats, opposite chairs have exactly 3 seats between them on either side.
Let's assign position numbers 1 to 8 in a clockwise direction.
If we place the block P−Q−R−S−T at positions 1 to 5 respectively, S is at position 4. For W to be opposite to S, W must be at position 8 (since 8−4=4).
This leaves positions 6 and 7 for U and V. Since V must be between U and W, V takes position 7 and U takes position 6.
Let's verify the clockwise condition:
- "While going in the clockwise direction around the table from P, one meets R before T".
In our arrangement (1:P, 2:Q, 3:R, 4:S, 5:T, 6:U, 7:V, 8:W), moving clockwise from P(1), we meet R(3) before T(5). This perfectly satisfies the condition!
(Note: If the arrangement was placed counter-clockwise, we would meet T before R, which would violate the rule).
Finding the final answer:
The question asks: "How many persons shall Q cross while moving in the clockwise direction around the table before meeting W?"
- Q is at position 2.
- W is at position 8.
- Moving clockwise from Q(2) to W(8), Q will pass by the persons sitting at positions 3, 4, 5, 6, and 7.
- These positions are occupied by R,S,T,U, and V.
Therefore, Q crosses exactly 5 persons before meeting W.