Question

A pair of unbiased dice is rolled simultaneously. Find the probability of getting a difference of at least three.

1. 1/3
2. 1/6
3. 1/9
4. 1/36
5. 1/12

Answer 1

Correct Answer - Option 1 : 1/3

Concept:

P(E) = Number of events/Number of possible outcomes

Calculations:

A pair of unbiased dice is rolled simultaneously 

So, the total possible outcomes = 6 × 6 = 36 

Total number of events of getting a difference of at least three = (1,4), (1,5), (1,6), (2,5), (2,6), (3,6), (4,1), (5,1), (5,2), (6,1), (6,2), (6,3) = 12

So, the probability of getting a difference of three = 12/36 = 1/3

∴ The probability of getting a difference of at least three is 1/3