Math Problem Statement

in a standard deck of 52 playing cards, a hand of 8 cards is drawn, how many hands have at least 2 queens

Solution

We are tasked with determining how many 8-card hands drawn from a standard 52-card deck contain at least 2 queens.

Steps to solve the problem:

  1. Total number of 8-card hands:
    The number of ways to select 8 cards from a deck of 52 cards (without any restrictions) is given by the combination formula: (528)\binom{52}{8} where (nr)\binom{n}{r} is the combination formula, nn is the total number of items, and rr is the number of items to choose.

  2. Hands with less than 2 queens: We need to calculate how many hands have fewer than 2 queens, i.e., either 0 or 1 queen.

    • Hands with 0 queens:
      There are 4 queens in the deck. If we exclude the queens, there are 48 non-queen cards remaining. We can select all 8 cards from these 48 non-queen cards: (488)\binom{48}{8}

    • Hands with exactly 1 queen:
      We first select 1 queen from the 4 available queens and then select the remaining 7 cards from the 48 non-queen cards: (41)×(487)\binom{4}{1} \times \binom{48}{7}

  3. Hands with at least 2 queens: To find the number of hands with at least 2 queens, we subtract the number of hands with fewer than 2 queens from the total number of hands: At least 2 queens=(528)((488)+(41)×(487))\text{At least 2 queens} = \binom{52}{8} - \left(\binom{48}{8} + \binom{4}{1} \times \binom{48}{7}\right)

Final Calculation:

Now, let's compute these values step by step.

  • (528)=52!8!(528)!=75287520\binom{52}{8} = \frac{52!}{8!(52-8)!} = 75287520
  • (488)=48!8!(488)!=75287520\binom{48}{8} = \frac{48!}{8!(48-8)!} = 75287520
  • (41)=4\binom{4}{1} = 4
  • (487)=48!7!(487)!=12271512\binom{48}{7} = \frac{48!}{7!(48-7)!} = 12271512

Now substitute these into the equation:

At least 2 queens=75287520(75287520+4×12271512)\text{At least 2 queens} = 75287520 - \left(75287520 + 4 \times 12271512\right) At least 2 queens=75287520(75287520+49086048)\text{At least 2 queens} = 75287520 - \left(75287520 + 49086048\right) At least 2 queens=75287520124573568\text{At least 2 queens} = 75287520 - 124573568 At least 2 queens=18520752\text{At least 2 queens} = 18520752

Thus, the number of 8-card hands with at least 2 queens is 18,520,752.

Let me know if you need more clarification or if you'd like to explore similar problems!

Additional Questions:

  1. How does the calculation change if you wanted a hand with at least 3 queens?
  2. How would the number of ways to select a hand change if you were restricted to only face cards (Jacks, Queens, Kings)?
  3. Can we use the same method to calculate hands with at least 2 cards of any specific rank (e.g., at least 2 Aces)?
  4. How does the concept of combinations change when selecting from a deck of cards with different distributions (e.g., decks with jokers)?
  5. What would happen if the deck size was increased from 52 to 60 cards?

Tip: When dealing with "at least" type problems, it's often easier to first calculate the total number of possibilities and then subtract the cases where the condition isn't met.

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Math Problem Analysis

Mathematical Concepts

Combinations
Probability
Combinatorics

Formulas

Combination formula: C(n, r) = n! / (r!(n - r)!)

Theorems

Inclusion-Exclusion Principle
Combination and permutation principles

Suitable Grade Level

Grades 10-12