Paper 2 · probability distributions
An unbiased die with faces marked 1, 2, 2, 3, 3, 3 is rolled twice. If X is the total score on the two rolls, what is P(X = 4), as a fraction out of 36?
A10/36
B9/36
C12/36
D6/36
Explanation: P(X=4) comes from the outcome pairs (1,3), (2,2), (3,1): P = (1/6)(3/6) + (2/6)(2/6) + (3/6)(1/6) = 3/36 + 4/36 + 3/36 = 10/36.
Derived from ZIMSEC Statistics Paper 2, November 2018, Q4
