Question

A box contains 5 red marbles and 7 green marbles. Find the probability of drawing 2 red marbles.

1. a) with replacement
2. b) without replacement

Answer 1

1. 25/144

2. 5/33

Explanation:

1. There are a total of 12 marbles. The probability of drawing the first marble red is: 5/12. Since we replace the marble, when we draw the second marble, the probability will also be 5/12. So we multiply them together and get: 25/144.

2. Again the probability of drawing the first marble red is 5/12. However, this time we're not replacing. This means that there are 12 - 1 = 11 remaining marbles and 5 - 1 = 4 remaining red marbles. Then the probability of choosing a second red marble is: 4/11. Multiply these two together: (5/12) * (4/11) = 20/132 = 5/33

Hope this helps!

Answer 2

1) 25/144 or 0.1736

2) 5/33 or 0.1515

Explanation:

Total marbles: 5 + 7 = 12

1) 5/12 × 5/12

25/144

0.173611111

2) 5/12 × 4/11

5/33

0.151515151515