Peter has two boxes of bricks, box A and box B.
Each box contains only red bricks, green bricks and yellow bricks.
In box A there are 15 bricks of which
5 are red,
7 are green,
and 3 are yellow.
In box B there are 20 bricks of which
8 are red,
9 are green,
and 3 are yellow.
Ami is going to take a brick at random from box A and a brick at random from box B.
She is going to put these two bricks on a table.
Calculate the probability that the two bricks on the table are different colours.
Peter has a third box of bricks, box C.
This box also contains only red bricks, green bricks and yellow bricks.
After taking a brick from box A and a brick from box B, Ami then takes at random a
brick from box C.
Ami then puts this brick with the other two bricks on the table.
The probability that there are three yellow bricks on the table is 19
1000