probability Qs~~~ (1 Viewer)

[Hikari Clover]

in 4 throws with a pair of dice, what is the probability that the sum of the numbers uppermost is 7 at least twice???

answer:19/144


thx~~~

 

[denoz]

probability of getting a sum of 7 is 1/6 therefore

4C2*(1/6)^2(5/6)^2 + 4C3*(1/6)^3(5/6)^1 + (1/6)^4=19/144 (hopefully)

(I don't have a calculator on me but im pretty sure its right)

 

[Marzaa]

Firstly I would find the probability that the sum will be seven in one throw i.e 1/6, i tend to use the addition table to find this.

Then i would express it as a binomial i.e. (1/6 + 5/6)^4 , since ur finding it for 4 throws and the 5/6 represents the chance that u won't get a 7

Hence u just find p(sum of 7 > 1) i.e 4C2.(1/6)^2.(5.6)^2 + 4C3.(1/6)^3.(5/6) + (1/6)^4 which should give u the answer (alternatively u can find the compliment where u find the probablity of not gettin a 7 and subtract from 1)