math
posted by Anonymous .
How do I approach this problem?
Seven green marbles and three red marbles are randomly placed in Box A and in Box B. Box A holds 4 marbles, while Box B holds 6. What is the probability that Box A has at least 2 green marbles?

There aren't that many cases
We can just list them , box A first, then Box B
GGGG GGGRRR
GGGR GGGGRR
GGRR GGGGGR
GRRR GGGGGG
Since the order does not matter, that is all
of these have 2 or more R's in boxA
so prob = 2/4 = 1/2 
It asked for at least 2 G's in A, should read more carefully.
so prob of 2 or more G's in box A is 3/4