Probability! (1 Viewer)

[0hNivlek]

Three people Patrice, Henry and Joel are comparing the months in which they were born.

i) show that the probablity that all three were born in different months is 55/72.

iii) Find the probability that exactly two people were born in the same month.


Thanks. Gah~ maths -___-.

 

[PC]

Patrice is born in a particular month.
The probability that Henry was born in a different month is 11/12.
The probability that Joel was born in a different month to Patrice AND Henry is 10/12.

Probability that all three born in a different month
= 1 x 11/12 x 10/12
= 55/72

 

[0hNivlek]

omg! I didn't think of it that way /slit!

THANKS!

 

[Timothy.Siu]

Three people Patrice, Henry and Joel are comparing the months in which they were born.

i) show that the probablity that all three were born in different months is 55/72.

iii) Find the probability that exactly two people were born in the same month.


Thanks. Gah~ maths -___-.

well, this is assuming theres an equal chance of being born in each month, which obviously isn't the case since not all months have the same numbers of days...but

first person is born in one of the 12 months, next person has a 11/12 chance of being born in a different month, 3rd person has a 10/12 chance of being born in a different month

11/12 x 10/12=55/72

3x1/12x11/12
theres 3 ways of grouping the 3 people together.
second person has a 1/12 chance of being born in the same month, then the next person cant be born in that month so 11/12

not very good explanations but yeah...