A box contains 3 blue counters and 8 red counters.
A counter is taken at random and its colour noted.
The counter is then set aside and not put back into the box.
A second counter is then taken at random, and its colour noted.
Write down the probability that
the second counter is red, given that the first counter was red
the second counter is blue, given that the first counter was red
the second counter is red, given that the first counter was blue
the second counter is blue, given that the first counter was blue.
If the first counter was red, then only 7 red counters remain in the box.
There are still 3 blue counters, and 10 counters in total.
If the first counter was red, then only 7 red counters remain in the box.
There are still 3 blue counters, and 10 counters in total.
If the first counter was blue, then only 2 blue counters remain in the box.
There are still 8 red counters, and 10 counters in total.
If the first counter was blue, then only 2 blue counters remain in the box.
There are still 8 red counters, and 10 counters in total.