Dice question (1 Viewer)

[lilkiwifruit]

This is a really stupid question which i can't work out...
A die is thrown 3 times what is the probability of throwing at least 2 sixes?

 

[lilkiwifruit]

*sinks to knees in despair* this is one of those easy questions that bugs you if u cant answer it ...

 

[kami]

This is a really stupid question which i can't work out...
A die is thrown 3 times what is the probability of throwing at least 2 sixes?

First throw: 1/6
Second throw: 1/6
Third throw: 5/6(remember there are five other options besides 6)
then just multiply each throw's chance and thats the answer.

 

[lilkiwifruit]

but the answer is 16/216...not 5/216 ...im so confused

 

[kami]

but the answer is 16/216...not 5/216 ...im so confused

oh crud, I've messed you up lol, sorry didnt read the "at least" so you add the possibility of the two sixes with the possibility of three sixes.

 

[lilkiwifruit]

Thank You

 

[webby234]

First throw: 1/6
Second throw: 1/6
Third throw: 5/6(remember there are five other options besides 6)
then just multiply each throw's chance and thats the answer.

You need to multiply by 3 as there are 3 different ways of getting 2 sixes.

So 3*1/6*1/6*5/6 = 15/216

+ (1/6)^3 = 16/216

 

[ephemeral]

Pr(atleast 2 sixes)= Pr(2 sixes)+Pr(3 sixes)

Using Binomial Distribution

Pr(2 sixes)= 3C2(1/6)^2(5/6) = 5/72
Pr(3 sixes)= 3C3(1/6)^3 = 1/216

(5/72)+(1/216)= 2/27 = 16/216 as required.

 

[webby234]

True, but that's a 3U topic.