# A jar contains four blue marbles and two red marble

+1 vote
a jar contains four blue marbles and two red marbles. suppose you choose a marble at random, and do NOT replace it. then you choose a second marble. find the probability of each event:
1. you select a blue marble and then a red marble
2. one of the marbles you select is blue and the other is red
3. you select two red marbles or two blue marbles

+1 vote

so you have a total of 6 marbles, chance of picking a blue is 4/6 and then a red is 2/5, so multiply the 2 probabilities together to get 8/30 for part one.

second part is a little more tricky, you need to add up the combined probabilities of each event occuring.  chance of getting blue marble first and then a red is 4/6 * 2/5, or 8/30 now add this to, the chance of getting a red and then blue which is 2/6 * 4/5= 8/30, add the 2 probabilities to get 16/30 as the probality of either occuring.

the third part is similar to the other parts.  chance of getting 2 reds is 2/6 * 1/6 which equals 2/36 add to probability of getting 2 blues which is 4/6*3/5=12/30.  now add 2/36 + 12/30 to get the total probablity
answered Jan 3, 2012 by anonymous
selected Jan 3, 2012
for the third part... the chance of getting 2 reds wont it be 2/6*1/5 because you get out a red causing the total to go from 6 to 5? so in the end the answer is 2/30*12/30?

+1 vote