Question

When rolling a die, determine the probability of rolling a number greater than 4.

Answer 1

Answer:

The probability that the result of one die roll is greater than 4 is the number of events in set A divided by the total number of possible outcomes (the size of the sample space S) and so the probability of getting a number greater than 4 on one die roll is  2/6  which reduces to  1/3 .

Step-by-step explanation:

Assuming you mean “greater”, rather than “greater than or equal to”, the “successful” rolls are 5 and 6. That’s two out of six choices, so the probability is 2/6 or 1/3.

It gets more interesting when you want the total of several dice to be above a certain number, or to get that number on M of N dice rolls.

But the two basic probability formulas work - 1) add up all possible successful results and all possible results, then divide the number of successes into the total. 2) Multiply all the failure probabilities together, then subtract the result from 1 (100%) to get the success probability. With these two rules, you can solve most simple probability problems.

Playing D&D, and want to know the chance of scoring a 17 or 18 total when rolling 3 dice? You can only get an 18 one way - 6 6 6. You can get a 17 three ways - 6 6 5, 6 5 6, or 5 6 6. So that’s 4 chances out of 6 x 6 x 6 possibilities, which is 216. That’s about 1.85%. With quite a bit more work, you can discover the chance of getting a 17 or better when rolling 4 dice and adding the 3 highest.