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Numerical Ability
Probability
A and B roll a pair of dice. A wins if he roll 6 and B wins if he rolls 7. They continue starting with A till one of them throws their respective number. What is the probability that A wins?
Read Solution (Total 8)
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- let getting6 event be x and getting7 event be y.
so, P(x)= 5/36 & P(y)= 6/36=1/6
P(x)complement = 1- 5/36 = 31/36
P(y)complement = 1- 6/36 = 5/6
let Z be winning probability
so, P(z)= 5/36 + 31/36.5/6.5/36 + 31/36.5/6.31/36.5/6.5/36 + .... infinity
= 30/61
- 10 years agoHelpfull: Yes(12) No(3)
- 5/36
6 can be rolled as 1,5 5,1 2,4 4,2 and 3,3 - 10 years agoHelpfull: Yes(5) No(1)
- let winning probability be p and losing probability be q.
A B
p=3/36;q=30/36; p=6/36;q=30/36;
P(Win A)=p+(q^2*p)+(q^2*q^2*p)+.....
taking p as common
P(Win A)=p[1+q^2+(q^2)^2+....)
terms are in GP
hence sum =p[1/(1-q^2)]
therefore general formula for prob of win A is p[1/(1-q^2)]
Since here losing probabilities are different we take
P(Win A)=p/[1-(q1*q2)]
=>(3/36)/[1-(33/36)(30/36)]
Solving this we get 13/24 - 10 years agoHelpfull: Yes(1) No(3)
- 1/6
6/36 becomes 1/6 - 10 years agoHelpfull: Yes(0) No(0)
- is it 2/3?
It is forming an infinte series... - 10 years agoHelpfull: Yes(0) No(0)
- two dice thrown sample space will be 36 and A's winning possibilties are 6
=> 6/36= 1/6.
what is the correct answer? - 10 years agoHelpfull: Yes(0) No(0)
- 1/2 correct answer
- 9 years agoHelpfull: Yes(0) No(0)
- There are 5 ways of obtaining 6 {(1,5), (5, 1), (2, 4), (4, 2), (3, 3)}
and Sample space while throwing 2 dice = 6×6 = 36
So P(E1)=5/36 and P(E1)=1−536=31/36
P(E2)=6/36 and P(E2)=1−16=5/6 - 9 years agoHelpfull: Yes(0) No(0)
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