Math - Statistics

posted by .

I roll 12 4-sided dice. What is the probability that I roll at least one 2? What is the probability that I roll exactly three 2s?

So i take it, on any give roll, the probability of rolling a 2 is .25 (25%); the probability of rolling something else must be .75

The probability of rolling at least one 2 is: one minus the probability of never rolling a two. And, with 12 chances, that probability is .75^12

To calculate the probability of rolling exactly three 2s, first count the numbe of ways can happen. That is, calculate 12-choose-3. This will be (10*11*12)/(1*2*3) = 220. So, the probability of rolling exactly three 2s will be 220*(.75^9)*(.25^3) = 25.8%

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Math - PLEASE

    I roll twelve 4-sided dice. What is the probability that I roll at least one 2?
  2. roll dice

    Event A you roll the die and it's even Event B you roll the die and it's less than 5 Roll the die once. What is the probability that Event A will occur given that Event B has alrady occured?
  3. statistics

    Roll 2 standard dice and add the numbers. whats the probability of getting a number Larger than 4 for the first time on the third roll?
  4. Algebra 2

    What is the probability when you roll 2 dice and you roll a number greater than 4 on the first dice and a 2 on the second dice?
  5. statistics

    The below table shows the probabilities generated by rolling one die 50 times and noting the up face. What is the probability of getting an odd up face?
  6. help!!!!! Probability!!!

    A fair 6-sided die is rolled twice. The probability that the second roll is strictly less than the first roll can be written as a/b, where a and b are positive, coprime integers. What is the value of a+b?
  7. probability

    We have two fair three-sided dice, indexed by i=1,2. Each die has sides labelled 1, 2, and 3. We roll the two dice independently, one roll for each die. For i=1,2, let the random variable Xi represent the result of the ith die, so …
  8. statistic

    Roll two 6-sided dice and examine their sum. a) How long will it take to roll "snake-eyes" (a pair of ones)?
  9. algebra

    Suppose that in a particular game two dice are tossed, and various amounts are paid according to the outcome. Find the requested probability. (Enter the probability as a fraction.) If a seven or an eight occurs on the first roll, the …
  10. Probability

    The newest invention of the 6.041x staff is a three-sided die. On any roll of this die, the result is 1 with probability 1/2, 2 with probability 1/4, and 3 with probability 1/4. Consider a sequence of six independent rolls of this …

More Similar Questions