SOLUTION: Suppose you are taking a 10--question quiz where each question has four possible answers. What's the probability that you will get at most 3 questions right?

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Question 1167457: Suppose you are taking a 10--question quiz where each question has four possible answers. What's the probability that you will get at most 3 questions right?
Answer by VFBundy(438) About Me  (Show Source):
You can put this solution on YOUR website!
Probability of getting exactly three questions right:
%280.25%29%5E3+%2A+%280.75%29%5E7+%2A+%2810%21%2F%283%21%2A7%21%29%29 = 0.2503

Probability of getting exactly two questions right:
%280.25%29%5E2+%2A+%280.75%29%5E8+%2A+%2810%21%2F%282%21%2A8%21%29%29 = 0.2816

Probability of getting exactly one question right:
%280.25%29%5E1+%2A+%280.75%29%5E9+%2A+%2810%21%2F%281%21%2A9%21%29%29 = 0.1877

Probability of getting exactly zero questions right:
%280.75%29%5E10 = 0.0563

Probability of getting "at most three" questions right:
0.2503 + 0.2816 + 0.1877 + 0.0563 = 0.7759