Question

A bag has 1 red marble, 4 blue marbles, and 3 green marbles. Peter draws a marble randomly from the bag, replaces it, and then draws another marble randomly. What is the probability of drawing 2 blue marbles in a row? Explain your answer.

Answer 1

To find the probability we will have to use the formula P= Desired Amount/ Total outcomes. Let's do the steps to solve this problem.

1. Substitute the known values..... The desired outcome is 4 since there are 4 blue marbles.

So our formula is now: 4/8>>>>> 8 is the total amount of marbles. 4/8 is equal to 1/2

2. This is a compound event since you are repeating a trial more than once. The compound formula states to multiply by the probability of the next event.

Peter did the experiment 2 times so you multiply 1/2 by 1/2.

3. 1/2 times 1/2=1/4. So the probability is 1/4 for Peter rolling a blue marble twice in a row.

Answer 2

The total number of marbles in the bag is 1 + 4 + 3 = 8

The probability of drawing one marble and getting blue is 4/8 = 1/2

Since marble is put back and he draws again, the probability will again be 1/2

The total probability = 1/2 * 1/2 = 1/4. 

1/4 <<<<Answer