Answer:2.86.
Explanation:
We can use the geometric distribution to solve this problem. The geometric distribution models the number of trials needed to achieve the first success in a sequence of independent trials with a constant probability of success.In this case, the probability of success (the teacher tripping over the cords) is 0.35. Therefore, the expected value or mean of the geometric distribution is 1/0.35 ≈ 2.86.So, on average, students need to wait for 2.86 periods until the teacher trips over the cords in her classroom.Therefore, the answer is 2.86.