The following cards are split into three piles at random, so that every pile contains the same number of cards. What is the probability that every pile contains an Ace?



Ace of spades

Ace of hearts

Ace of diamonds

Ace of clubs

Two of spades

Two of hearts

Bot GPT-4o Bot GPT-4o answered
2 days ago

To solve the problem of determining the probability that every pile contains an Ace when the given cards are split into three piles randomly, we need to proceed through a series of logical and combinatorial steps. The deck in question contains the following 6 cards:

- Ace of spades
- Ace of hearts
- Ace of diamonds
- Ace of clubs
- Two of spades
- Two of hearts

### Total Arrangements
Firstly, we calculate the total number of ways to distribute these 6 cards into 3 piles with each pile having 2 cards.

\[ \text{Number of ways to choose 2 cards out of 6 for the first pile} = \binom{6}{2} \]
\[ \text{Number of ways to choose 2 cards out of remaining 4 for the second pile} = \binom{4}{2} \]
\[ \text{Remaining 2 cards go to the third pile automatically} \]

Using the binomial coefficient formula:
\[ \binom{6}{2} = \frac{6!}{2!(6-2)!} = \frac{6 \times 5}{2 \times 1} = 15 \]
\[ \binom{4}{2} = \frac{4!}{2!2!} = \frac{4 \times 3}{2 \times 1} = 6 \]
\[ \binom{2}{2} = 1 \]

Since the order in which we choose the piles doesn't matter, we must divide by the number of permutations of the 3 piles to avoid double-counting:
\[ \frac{15 \times 6 \times 1}{3!} = \frac{15 \times 6}{6} = 15 \]

Thus, there are 15 different ways to distribute the 6 cards into 3 piles each containing 2 cards.

### Favorable Cases
Now, we need to count the number of favorable cases where each of the 3 piles has exactly one Ace. Since there are 4 Aces and 2 non-Ace cards, at least one pile must contain both non-Ace cards while the other two contain one Ace each along with a non-Ace.

To accomplish this:
1. Select one pile to contain the two non-Aces.
- There is 1 way to place the two non-Aces: choosing the two from the two non-Aces is trivial.

2. Distribute the 4 Aces into the remaining two piles such that each pile gets exactly two Aces.

We can count this as follows:
- Choose 2 out of 4 Aces for one pile (\(\binom{4}{2}\)).

Calculating:
\[ \binom{4}{2} = \frac{4!}{2!2!} = 6 \]

Thus, there are 6 favorable ways to ensure each pile ends up with exactly one Ace.

### Probability Calculation
Finally, the probability is the ratio of favorable outcomes to total possible outcomes:
\[ P(\text{Each pile contains an Ace}) = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} = \frac{6}{15} = \frac{2}{5} \]

Therefore, the probability that every pile contains an Ace is \(\boxed{\frac{2}{5}}\).

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