Question 1026565
a bag contains two black balls, three green balls and four 
red balls. 
<pre>
That's a total of 2 blacks + 3 greens + 4 reds = 9 balls
</pre>
A ball is picked from the bag at random. What
is the probability that it is;
1. black
<pre>
That's 2 black balls out of 9 balls, so the probability is 2/9.
That doesn't reduce so we leave it 2/9. 
</pre>
2. green
<pre>
That's 3 green balls out of 9 balls, so the probability is 3/9.
That reduces to 1/3
</pre>
3. red
<pre>
That's 4 red balls out of 9 balls, so the probability is 4/9.
That doesn't reduce so we leave it 4/9. 
</pre>
4. yellow
<pre>
There are no yellow balls in the bag.
That's 0 yellow balls out of 9 balls, so the probability is 0/9,
which is just 0.  When something is impossible, its probability
is 0.
</pre>
5. not black
<pre>
There are 3+4 or 7 balls that are not black, because 3 are green
and 4 are red.
That's 7 non-black balls out of 9 balls, so the probability is 7/9.
That doesn't reduce so we leave it 7/9.
</pre>
6. either black or red?
<pre>
There are 2+4 or 6 balls that are either black or red, because 2 
are black and 4 are red.
That's 6 black or red balls out of 9 balls, so the probability 
is 6/9.  That reduces to 2/3.

Edwin</pre>