Seven green marbles and seven brown marbles which are indistinguishable apart from color are placed in a box. If Liza takes out 4 marbles randomly from the box, find the probability of there being 2 green marbles and 2 brown marbles.

Can someone direct me to a place that shows me how to do questions like this or explain it to me? Thanks.

Question

Seven green marbles and seven brown marbles which are indistinguishable apart from color are placed in a box. If Liza takes out 4 marbles randomly from the box, find the probability of there being 2 green marbles and 2 brown marbles.

Can someone direct me to a place that shows me how to do questions like this or explain it to me? Thanks.

amistre64 · Answer

determine the probability at each step; and multiply them together

anonymous · Answer

try purplemath.com and type in probability.

anonymous · Answer

http://www.mathleague.com/help/percent/percent.htm#whatisanevent Scroll down to 'Probability of an Outcome'

amistre64 · Answer

14 total

prob of a green is 7/14
prob of next green is 6/13
prob of next brown is 7/12
prob of next brown is 6/11

anonymous · Answer

Thanks. I did what amistre64 said, but I got a different answer than the answer key. I thought maybe it was me.

amistre64 · Answer

probability of green and green and brown and brown
$$\frac{7*7*6*6}{14*13*12*11}$$
right?

anonymous · Answer

So, 21/286 or about 0.07 is correct?

amistre64 · Answer

yep; as long as im recalling it right :)

anonymous · Answer

Seven green marbles and seven brown marbles which are indistinguishable apart from color are placed in a box. If Liza takes out 4 marbles randomly from the box, find the probability that the fourth marble is green if the first three were brown.

I think that makes the answer 7/11 and a better level for younger students.