iliavko wrote:
Bunuel, Karishima, someone please!
I don't understand the Combinations method, it makes no sense to me what so ever.
So I am trying to use Venn diagram here.
So: P(N)+P(G)-P(N and G) = 1
G-George N-nina We want to know George only, so no Nina and no overlap George plus Nina.
P(N)=1-P(not N) \(1- \frac{7}{8}*\frac{6}{7}*\frac{5}{6} = \frac{3}{8}\)
P(G)=1-P(not G) \(1- \frac{6}{7}*\frac{5}{6}*\frac{4}{5} = \frac{3}{7}\)
P(N and G)= P(A) * P(B) \(\frac{9}{56}\)
So: 1-P(N)+P(N and G) = P(G)
\(1-\frac{56}{56}-\frac{21}{56}+\frac{9}{56}\) SHOULD BE P(G), but it's \(\frac{26}{56}\)
How come????? What is wrong here?...
Thanks!
Hi iliavko,
Why are you using Venn diagram ?
This tool is rather used for sets questions. OK ?
The question asks the probability of choosing a group of 3 people from 8, including A and excluding B.
So, the basic proba formula is P = (Number of outcomes where the event occurs) / (Number total of outcomes)
Number of outcomes where the event occursStage 1 : Number oy ways to choose A = 1
Stage 2 : Number of ways to choose 2 people form 6 (8, minus A, minus B since you want A and no B) = 15
Number of outcomes where the event occurs = 15
Number total of outcomesNumber of ways choose 3 people from 8 = 56
So P = 15/56
OK ?