Tommy has a piece of toast that has butter on one side, and he dropped it twice. both times, it landed with the butter side up. if he drops it 2 more times, what is the probability that it will have landed butter side up a total of 3 times?

1/2.

Explanation:

First, note that since the previous drops have already happened, their result do not modify the occurrence of future results when the toast is dropped again.

In oder to have a total of three time landing butter side up, exactly, there are two possibilities:

Since there are two ways of totaling side up 3 times, you have to sum both chances.

1) Next drop butter side up and second drop butter side down:

     1/2 × 1/2  = 1/4

2) Next drop butter side down and second one butter side up:

     1/2 × 1/2 = 1/4

3) Add both probabilities: 1/4 + 1/4 = 1/2

And that is the 1/2

answer: the answer is 35%

the expected value of the random variable : 0, 1 and 2

step-by-step explanation: