Latest TCS Aptitude Question SOLUTION: A pair of fair dices rolled together till a sum of either 5 or 7 is obtained what is the probability that 5 comes before 7?

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A pair of fair dices rolled together till a sum of either 5 or 7 is obtained what is the probability that 5 comes before 7?

Asked In TCS NIKHIL KAPARABOINA (10 years ago)

Unsolved Read Solution (4)

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sakshi ajay  (10 years ago)

Event when sum is 5 or 7,E1=(1,4),(1,6),(2,3),(2,5),(3,2),(3,4),(4,1),(4,3),(5,2),(6,1)
n(E1)=10
Event when 5 comes before 7,E2=(1,4),(2,3),(3,2),(4,1)
n(e2)=4
So,P(E2)/P(E1)=n(E2)/n(E1)=4/10=2/5

Is this solution Helpfull? Yes (32) | No (3)  

ARUN GUPTA  (10 years ago)

5 = (1,4),(2,3),(3,2),(4,1)
7 = (1,6),(2,5),(3,4),(4,3),(5,2),(6,1)
n(S)= 4+6=10
n(E)= 4
p(E)= 4/10 = 2/5

Is this solution Helpfull? Yes (8) | No (4)  

kratika jain  (10 years ago)

Let A=P(sum=5)=4/36 {(1,4) (4,1) (2,3) (3,2)}
B=P(sum=7)=6/36 {(6,1) (1,6) (2,5) (5,2) (3,4) (4,3)}
C=P(sum other than 5 or 7) 1-(10/36)=26/36
P(sum 5 comes b4 7)=P(5)+P(C)P(5)+P(C)P(C)P(5)....
=4/36(1+26/36+(26/36)^2+(26/36)^3......)
=4/36*1/(1-26/36)=(4/36)*(36/10)=2/5
thus ans=2/5

Is this solution Helpfull? Yes (2) | No (1)  

Guru Pranav  (10 years ago)

total ways of getting =4, total ways of getting 7=6

so, Probability of 5 before 7 = 4/10 Ans

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