IKMC 2010 - Grades 11-12 - Paper 02 - Self-study Question 23

Question 23

An ordinary fair die is rolled “once”, according to the source wording. Given that the third result equals the sum of the first two, what is the probability that a 2 appeared at least once?

Editorial correction: “once” is inconsistent with the first, second and third results. Use three independent rolls for this scored question.

$1/6$
$91/216$
$1/2$
$8/15$
$7/12$