The Deuce
[ Message Archive | The Deuce ]

    It got that. Highlighted in bold in the quoted text. Archived Message

    Posted by GrandmotherPearlsJam on February 23, 2025, 14:02:43, in reply to "Rolling 3 dice and getting all the same is not 1/6... It's 6/216, or 1/36.*"

    It got the same percentages as you.
    Previous Message

    Previous Message

    Let's calculate the probability of rolling **three of a kind** using **three dice** and **four dice** to determine how much the odds increase.

    ### **Case 1: Rolling 3 Dice**
    We need exactly **three** dice to show the same number.

    1. Pick a number (1-6) that will be the triplet → Probability = \( \frac{1}{6} \).
    2. The first die can be any number → Probability = \(1\).
    3. The second die must match the first → Probability = \( \frac{1}{6} \).
    4. The third die must also match → Probability = \( \frac{1}{6} \).

    Thus, the probability of rolling three of a kind exactly is:
    \[
    6 \times \left(\frac{1}{6} \times \frac{1}{6}\right) = \frac{6}{36} = \frac{1}{6} \approx 16.67\%
    \]

    ### **Case 2: Rolling 4 Dice**
    We need at least **three** of the four dice to show the same number.

    #### **Scenario 1: Exactly 3 Matching, 1 Different**
    1. Pick the matching number (1-6) → \( \frac{1}{6} \).
    2. Choose which three dice will match (ways to choose 3 out of 4) → \( \binom{4}{3} = 4 \).
    3. The three matching dice each roll that number → \( \left(\frac{1}{6}\right)^2 \).
    4. The fourth die rolls a different number (5 choices) → \( \frac{5}{6} \).

    \[
    6 \times 4 \times \left(\frac{1}{6} \times \frac{1}{6}\right) \times \frac{5}{6} = \frac{120}{1296} \approx 9.26\%
    \]

    #### **Scenario 2: All 4 Matching**
    1. Pick the number → \( \frac{1}{6} \).
    2. All four dice must roll that number → \( \left(\frac{1}{6}\right)^3 \).

    \[
    6 \times \left(\frac{1}{6} \times \frac{1}{6} \times \frac{1}{6}\right) = \frac{6}{216} = \frac{1}{36} \approx 2.78\%
    \]


    ### **Total Probability (Rolling 4 Dice)**
    Adding both scenarios together:

    \[
    9.26\% + 2.78\% = 12.04\% \text{ (extra chance with 4th die)}
    \]

    \[
    16.67\% + 12.04\% = 28.7\%
    \]

    ### **Odds Increase**
    \[
    \frac{28.7\%}{16.67\%} \approx 1.72
    \]

    So, rolling **4 dice instead of 3 increases your odds by about 72%** of rolling three of a kind.


    Message Thread: