Question

A bag contains 3 red marbles, 7 white marbles, and 5 blue marbles. You draw 3 marbles, replacing each one before drawing the next. What is the probability of drawing a red, then a blue, and then a white marble?

Answer 1

7/225

Explanation:

To find probability, we take the number of ways the specific event can occur and divide it by the number of ways any event can occur.

The probability of drawing a red marble is: (# of red marbles) / (total # of marbles) = 3/(3 + 7 + 5) = 3/15 = 1/5.

The probability of drawing a blue marble is: (# of blue marbles) / (total # of marbles) = 5/(3 + 7 + 5) = 5/15 = 1/3.

The probability of drawing a white marble is: (# of white marbles) / (total # of marbles) = 7/(3 + 7 + 5) = 7/15.

Now, we want these events to all occur for us. So, we must multiply them by each other: (1/5) * (1/3) * (7/15) = 7/225.

Thus, the probability is 7/225.

Hope this helps!

Answer 2

3 + 7 + 5 = 15 total marbles.

3 red, picking a red would be 3/15, reduced to 1/5

5 blue, picking a blue would be 5/15, reduced to 1/3

7 white, picking a white would be 7/15

Picking all 3 would be: 1/5 x 1/3 x 7/15 = 7/225