Read the following information carefully and answer the questions that follow.

Eight athletes P, Q, R, S, U, W, K and M participated in a running race, with each finishing in a unique position. W finished last. U finished immediately ahead of W and immediately behind Q. R finished ahead of K, but behind no other runner. M finished ahead of S but behind P, while K finished ahead of P.

How many athletes finished ahead of S?

The correct answer is 4.

Step-by-Step Explanation:

Let us arrange the 8 athletes (P, Q, R, S, U, W, K, and M) in order of their finishing positions from 1st (first place) to 8th (last place) based on the clues provided:

1. Total Athletes: There are 8 finishing positions, numbered 1 to 8.

2. Clue 1: "W finished last."
This means W is at position 8.
Order: _ , _ , _ , _ , _ , _ , _ , W(8th)

3. Clue 2: "U finished immediately ahead of W and immediately behind Q."
Since W is 8th, U must be 7th, and Q must be 6th.
Order: _ , _ , _ , _ , _ , Q(6th) , U(7th) , W(8th)

4. Clue 3: "R finished ahead of K, but behind no other runner."
Finishing "behind no other runner" means R came in 1st place.
Order: R(1st) , _ , _ , _ , _ , Q(6th) , U(7th) , W(8th)

5. Clue 4: "M finished ahead of S but behind P, while K finished ahead of P."
Let us analyze the relative order of the remaining athletes (K, P, M, S):
- K is ahead of P (K > P)
- P is ahead of M (P > M)
- M is ahead of S (M > S)
Combining these gives the exact order: K > P > M > S.

6. Positions 2 through 5:
The remaining available positions are 2, 3, 4, and 5.
Placing K, P, M, S in order into these positions:
- 1st position: R
- 2nd position: K
- 3rd position: P
- 4th position: M
- 5th position: S
- 6th position: Q
- 7th position: U
- 8th position: W

Complete Finishing Order:
1st: R
2nd: K
3rd: P
4th: M
5th: S
6th: Q
7th: U
8th: W

Answering the Question:
The question asks: "How many athletes finished ahead of S?"
S finished in 5th position, which means the athletes who finished ahead of S are R, K, P, and M.

Thus, exactly 4 athletes finished ahead of S.