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
asked Jan 3, 2012 in Mathematics by anonymous

1 Answer

+1 vote
Best answer
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 by pokemonmaster
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?

Related questions

0 votes
1 answer 41 views
41 views asked Mar 12, 2013 in Earth Science by anonymous