Cab you please explain the first part of this approach?
P(l) = 15/500
P(b) = 15/800
Why did you put 15 students in each school?
It talks about 30 pairs of siblings, so there are 60 students.
So each school has 30 students who have siblings in the other school, no?
Thank you for the help, I just confused by the 15 number.
Carcass wrote:
1st - you need to pick on from any school, who has a sibling
P(l) = 15/500
P(b) = 15/800
2nd - you need to pick his pair sibling from the other school
P(b-l) = 1/800
P9l-b) = 1/500
3rd, you need to multiply resepectively ("AND" - for example - both P(l) and P(b-l) needed) and sum the result ("OR", one of the options needed)
1. 15/500*1/800 = 15/400,000
2. 15/800*1/500 = 15/400,000
1+2. = 15/400,000 +15/400,000 = 30/400,000 = 3/40,000