Math Problem Statement

A poker hand consisting of 8 cards is dealt from a standard deck of 52 cards.

Find the probability that the hand contains exactly 4 face cards. Leave your answer as a reduced fraction.

The probability is

Solution

To solve this problem, we need to calculate the probability of being dealt exactly 4 face cards in an 8-card poker hand from a standard deck of 52 cards.

Step 1: Determine the total number of possible hands

The number of ways to choose 8 cards from a deck of 52 cards is given by the combination formula:

(528)=52!8!(528)!=(528)\binom{52}{8} = \frac{52!}{8!(52-8)!} = \binom{52}{8}

Step 2: Determine the number of successful hands (hands with exactly 4 face cards)

There are 12 face cards in a deck (4 Jacks, 4 Queens, and 4 Kings). We want to choose exactly 4 of these 12 face cards. The number of ways to choose 4 face cards from 12 is:

(124)=12!4!(124)!=(124)\binom{12}{4} = \frac{12!}{4!(12-4)!} = \binom{12}{4}

The remaining 4 cards must come from the 40 non-face cards in the deck. The number of ways to choose 4 non-face cards from the 40 non-face cards is:

(404)=40!4!(404)!=(404)\binom{40}{4} = \frac{40!}{4!(40-4)!} = \binom{40}{4}

Step 3: Calculate the probability

The probability of getting exactly 4 face cards is the ratio of the number of successful hands to the total number of possible hands. This can be expressed as:

Probability=(124)(404)(528)\text{Probability} = \frac{\binom{12}{4} \cdot \binom{40}{4}}{\binom{52}{8}}

Now, let's calculate the combinations and simplify.

Calculations:

(124)=12×11×10×94×3×2×1=495\binom{12}{4} = \frac{12 \times 11 \times 10 \times 9}{4 \times 3 \times 2 \times 1} = 495 (404)=40×39×38×374×3×2×1=91,390\binom{40}{4} = \frac{40 \times 39 \times 38 \times 37}{4 \times 3 \times 2 \times 1} = 91,390 (528)=52×51×50×49×48×47×46×458×7×6×5×4×3×2×1=752,875,680\binom{52}{8} = \frac{52 \times 51 \times 50 \times 49 \times 48 \times 47 \times 46 \times 45}{8 \times 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1} = 752,875,680

Now, calculate the probability:

Probability=495×91,390752,875,680=45,276,050752,875,680\text{Probability} = \frac{495 \times 91,390}{752,875,680} = \frac{45,276,050}{752,875,680}

Simplifying the fraction:

[ \text{Probability} = \frac{226,38025}{376,437,840} = \frac{22635}{18821892} \

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Math Problem Analysis

Mathematical Concepts

Combinatorics
Probability
Card Combinations

Formulas

Combination formula: C(n, k) = n! / (k!(n-k)!)
Probability formula: P = (successful outcomes) / (total outcomes)

Theorems

Basic Probability Theorem
Combination Formula

Suitable Grade Level

Grades 11-12