Multiple choice

A fair die is thrown until a score of less than $5$ points obtained. The probability of obtaining not less than $2$ points on the last thrown is

  1. $\displaystyle\frac { 3 }{ 4 } $
  2. $\displaystyle\frac { 5 }{ 6 } $
  3. $\displaystyle\frac { 4 }{ 5 } $
  4. $\displaystyle\frac { 1 }{ 2 } $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The stopping score is uniformly one of 1, 2, 3, or 4, because the process stops at the first score below 5. Three of these four possible final scores are at least 2, so the probability is 3/4.

AI explanation

The experiment ends when a score of less than 5 is obtained, meaning the final roll must be a 1, 2, 3, or 4, giving four possible successful ending values. The problem asks for the probability that the final roll is not less than 2, which restricts the successful ending values to 2, 3, or 4. Using the definition of conditional probability, the desired probability is the 3 successful values divided by the 4 total ending values, resulting in 3/4.

Keep practicing — related questions