In the SuperLottery, three balls are drawn (at random, without replacement) from white balls numbered from $1$ to $10,$ and one SuperBall is drawn (at random) from red balls numbered from $11$ to $20.$ When you buy a ticket, you choose three numbers from $1$ to $10,$ and one number from $11$ to $20.$



If the numbers on your ticket match the three white balls and the red SuperBall, then you win the jackpot. (You don't need to match the white balls in order). What is the probability that you win the jackpot?

1 answer

To determine the probability of winning the jackpot in the SuperLottery, we will first calculate the total number of ways to select the balls and then the number of winning selections.

  1. Choosing the white balls: We need to choose 3 balls from a total of 10 white balls. The number of ways to choose 3 balls from 10 can be calculated using the binomial coefficient, given by:

    \[ \binom{10}{3} = \frac{10!}{3!(10-3)!} = \frac{10 \times 9 \times 8}{3 \times 2 \times 1} = 120. \]

  2. Choosing the SuperBall: There is only 1 SuperBall selected from 10 possible balls (numbered from 11 to 20). Thus, the number of ways to choose the SuperBall is simply:

    \[ \binom{10}{1} = 10. \]

  3. Total combinations of drawing the balls: The total number of possible combinations of the lottery draw (3 white balls and 1 SuperBall) can be calculated by multiplying the combinations of the white balls and the SuperBall:

    \[ \text{Total combinations} = \binom{10}{3} \cdot \binom{10}{1} = 120 \times 10 = 1200. \]

  4. Winning combinations: To win the jackpot, all selected numbers on the ticket must match the drawn balls. There is exactly 1 way to win, which is by matching the specific combination of the 3 white balls and the 1 SuperBall drawn.

  5. Calculating the probability: The probability of winning can be expressed as the fraction of winning combinations to the total combinations:

    \[ P(\text{win}) = \frac{\text{Winning combinations}}{\text{Total combinations}} = \frac{1}{1200}. \]

Thus, the probability that you win the jackpot is

\[ \boxed{\frac{1}{1200}}. \]