Two unbiased dice are rolled simultaneously. Find the probability of g...
Given:
Number of unbiased dice = 2
Concept:
Probability (Event) = Number of favorable outcome / Total outcome
Calculation:
No. of ways of rolling a pair of dice = 6 × 6 = 36
Let E = event of getting a sum greater than 5 = {(1, 6), (1, 5), (2, 6),(2, 5), (2, 4), (3, 6), (3, 5), (3, 4), (3, 3), (4, 6), (4, 5), (4, 4), (4, 3), (4, 2), (5, 6), (5, 5),(5, 4), (5, 3), (5, 2), (5, 1), (6, 6), (6, 5), (6, 4), (6, 3), (6, 2), (6,1)}
n(E) = 26
⇒ Required probability = 26/36 = 13/18
⇒ The probability of getting sum greater than 5 = 13/18
Alternate Method:
Given:
Number of unbiased dice = 2
Concept:
Probability (Event) = 1 - (Number of non favorable outcome / Total outcome)
Probability of getting a sum greater than 5 = 1 - (Probability of getting a sum less than or equal to 5)
Calculation:
No. of ways of rolling a pair of dice = 6 × 6 = 36
Let F = event of getting a sum less than or equal to 5 = {(1, 1), (1, 2), (1, 3), (1, 4), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (4,1)}
n(F) = 10
⇒ Required probability = 1 - (10/36) = 1 - (5/18) = 13/18
∴ The probability of getting sum greater than 5 = 13/18
Important Points
When we have a large number of cases like 26 in case of Event (E) then we calculate non-favorable outcome(Compliment event i.e. 1 - favourable event)
Mistake Points
In this question, we have to avoid the cases in which sum of digit is equal to five like{(1, 4),(2, 3),(3, 2),(4,1)}
Additional Information
Probabilities for the two dice