Quote:
Originally Posted by jay_shark
If the events are independent, then the probability that either event occurs is
30/31 + 19/20 - 30/31*19/20 = 619/620
The odds in favor of either event occuring is 619 : 1
This uses the well known formula
P(A or B) = P(A) + P(B) - P(A and B)
I tested this formula but came up with a very different result.
30/31 + 19/20 - 30/31*19/20 = 619/620
30/31 +19/20=for a total of 49/51 for the first part of the equation
or another result 30/31=.968 and 19/20=.95 (.968+.95)=1.918 not sure which approach is correct.
the second part is 30/31 * 19/20 which I multiplied to get a result of 30*19=570 and 31*20=620 making the 2nd fraction 570/620
the way the problem appears to be set up is (a+b) - (a * b) but how does one come up with the top numerator of 619? 30*19=570, only when one adds the 30 and 19 to the 570 does one come up with a numerator of 619, however going by the formula shouldn't I be subtracting 570/620 from 49/51?
to make the equation look like this 49/51-570/620 ??
30/31 + 19/20 - 30/31*19/20 = 619/620 <-- how does one solve this math problem??? Or how does one set it up to come up with that result?
Appreciate any help
txsransom04