Problem Analysis #25

EXAONE-4.0.1-32B (high) · Run 1

3.91s
3,480 toks
Problem Statement

Suppose the following conditions hold. A prize-drawing event uses a box containing 4 crimson balls and 5 blue balls. You are given four opportunities to draw a ball, without replacement.Under these conditions, you receive a prize of 100(10,000-won units) if you draw a crimson ball on the first draw, and 200(10,000-won units) if you draw a crimson ball on the fourth draw. Let XX be the random variable representing the total prize money obtained after drawing four balls from the box. If the expected value of XX is written as

pq,\frac{p}{q},

where pp and qq are relatively prime positive integers, find the value of

pq2.p \cdot q^2.

oindent

Ground Truth
3600
Execution Trace
Reasoning Process

[THOUGHT] To find the expected value of the total prize money XX, we need to consider the probabilities of drawing a crimson ball on the first and fourth draws. The prize for drawing a crimson ball on the first draw is 100 units, and for the fourth draw is 200 units. The expected value E[X]E[X] is the sum of the expected prizes from these two events.

  1. First Draw: The probability of drawing a crimson ball on the first draw is 49\frac{4}{9}, and the prize is 100 units. The expected prize from the first draw is 100×49100 \times \frac{4}{9}.

  2. Fourth Draw: The probability of drawing a crimson ball on the fourth draw is more complex because it depends on the outcomes of the first three draws. However, by symmetry, the probability of drawing a crimson ball on any specific draw (including the fourth) is the same as the first draw, which is 49\frac{4}{9}. The expected prize from the fourth draw is 200×49200 \times \frac{4}{9}.

Thus, the total expected value E[X]E[X] is:

E[X]=100×49+200×49=4009+8009=12009=4003.E[X] = 100 \times \frac{4}{9} + 200 \times \frac{4}{9} = \frac{400}{9} + \frac{800}{9} = \frac{1200}{9} = \frac{400}{3}.

The fraction 4003\frac{400}{3} is already in its simplest form, so p=400p = 400 and q=3q = 3. The value of pq2p \cdot q^2 is 400×32=400×9=3600400 \times 3^2 = 400 \times 9 = 3600.

[/THOUGHT] [PYTHON]

Verification of the expected value calculation

from fractions import Fraction

Probability of crimson on first draw

prob_first = Fraction(4, 9) prize_first = 100

Probability of crimson on fourth draw (same as first due to symmetry)

prob_fourth = Fraction(4, 9) prize_fourth = 200

Expected value calculation

E_X = prize_first * prob_first + prize_fourth * prob_fourth p = E_X.numerator q = E_X.denominator result = p * q * q

print(result) [/PYTHON]

Tool Output
[PYTHON OUTPUT] 3600 [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] The Python output confirms that the expected value calculation is correct, yielding pq2=3600p \cdot q^2 = 3600.

[/THOUGHT] 3600\boxed{3600}

Final Model Output
3600

Comparative Analysis (P25) (Average across runs)

Avg Time Taken

K-EXAONE-236B-A23B
164.4
Kanana-2-30B-Thinking
45.3
Gemini-3-Pro-Preview
35.8
Grok-4.1-fast
31.5
K-EXAONE-236B-A23B
28.9
HCX-007(high)
28.2
Deepseek-V3.2
27.9
Llama-VARCO-8B-Instruct
27.7
Solar-Pro-2 (31B)(high)
24.3
Kanana-2-30B-Thinking-2601
19.0
Solar-Open-100B
16.4
Claude-Opus-4.5
14.3
A.X-4.0 (72B)
13.5
GPT-5.1 (high)
13.4
GPT-5.2 (high)
11.4
EXAONE-4.0.1-32B (high)
3.9

Avg Token Usage

K-EXAONE-236B-A23B
18,548
Kanana-2-30B-Thinking
9,068
Kanana-2-30B-Thinking-2601
5,759
Gemini-3-Pro-Preview
5,595
Grok-4.1-fast
5,445
Solar-Pro-2 (31B)(high)
5,220
Solar-Open-100B
4,781
K-EXAONE-236B-A23B
4,410
HCX-007(high)
4,007
Claude-Opus-4.5
3,853
Deepseek-V3.2
3,682
EXAONE-4.0.1-32B (high)
3,480
GPT-5.2 (high)
3,140
GPT-5.1 (high)
2,933
Llama-VARCO-8B-Instruct
1,847
A.X-4.0 (72B)
1,715