# Bicking a Black Molly or Neon

• January 25th 2011, 10:28 AM
dwsmith
Bicking a Black Molly or Neon
I can't obtain the answer (5/6) to this question.

Four species of fish--BM, G, GF, and N-- are available in a fish store:. A child has been told that she may choose any two of these fish species for her aquarium. Then several fish of each species will be purchased. Suppose that she is equally likely to chooses each species.

She has either a BM or a N but not both.

First pick is 1/2 and the second is 2/3 but this isn't right.
• January 25th 2011, 10:44 AM
Plato
Quote:

Originally Posted by dwsmith
I can't obtain the answer (5/6) to this question.
Four species of fish--BM, G, GF, and N-- are available in a fish store:. A child has been told that she may choose any two of these fish species for her aquarium. Then several fish of each species will be purchased. Suppose that she is equally likely to chooses each species.
She has either a BM or a N but not both.

Why do you think the answer is $\frac{5}{6}~?$
There are six ways to pick two species.
Here are the outcomes you want: $\left\{\{Bm,G\},\{N,G\},\{Bm,GF\},\{N,GF\}\right\}$.
There are four not five.
• January 25th 2011, 10:46 AM
dwsmith
Quote:

Originally Posted by Plato
Why do you think the answer is $\frac{5}{6}~?$
There are six ways to pick two species.
Here are the outcomes you want: $\left\{\{Bm,G\},\{N,G\},\{Bm,GF\},\{N,GF\}\right\}$.
There are four not five.

The book told me 5/6.
• January 25th 2011, 10:50 AM
Plato
Quote:

Originally Posted by dwsmith
The book told me 5/6.

That is the answer to not both BM & N.
It is not the answer to either BM or N but not both.
• January 25th 2011, 10:57 AM
dwsmith
Quote:

Originally Posted by Plato
That is the answer to not both BM & N.
It is not the answer to either BM or N but not both.

Ok, I see what you mean since the sample space is $\left\{(BM,G),\ (BM,GF), \ (BM,N), \ (G,GF), \ (G,N), \ (GF,N)\right\}$

5/6 includes (G,GF).

The solution is then 4/6 = 2/3