# 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%

## Similar Questions

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