lost in probability

[shano1239]

I know the basic stuff in probability, just certain questions confuse me where I have to multiply two different fractions. I have two differnet questions that I would like to have help on . Questions;

(A) two dice are rolled . What is the probability that the sum of the numbers rolled are (a) 4? (b) a number greater then 9?

(B)rn contains 6 green marbles and 6 yellow marbles. Two marbles are drawn at random. What is the probability that the first one is green and the second is yellow if the marbles are drawn
(a) with replacement? (b) without replacement?

Thank you
~Shannon

 

[stapel]

A) Draw the six-by-six grid, labelling along the top and left with the values that each cube could display. Inside the grid, enter the sums of the two values. (So the top-left entry would be 1 + 1 = 2, and the bottom-right entry would be 6 + 6 = 12.)

a) How many of these thirty-six entries are "4"? So what is the probability?

b) How many are 10, 11, or 12? So what is the probability?

B) How many total marbles are there? How many are green? So what is the probability of drawing a green? How many are yellow? So what is the probability of drawing a yellow?

a) Since the first marble does not influence the choice of the second marble, just multiply the probabilities of the two (independent) events.

b) What is the probability of the first marble (drawn from the full twelve) being green? Now that you have eleven (five green and six yellow), what is the probability of drawing a yellow? Multiply.

Eliz.

 

[shano1239]

Thank you, Thank you, Thank you!!