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Random Variables, Expectation & Variance · Question 12 of 68

What is the probability of at least one tail in the four tosses?

Question 12

MediumOriginal question

Four fair coins are tossed together, and XX is the number of tails that show.

What is the probability of at least one tail in the four tosses?

Options for question 12

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. The only way to get no tail is HHHH, with probability 116\frac{1}{16}.

  2. 1−116=15161 - \frac{1}{16} = \frac{15}{16}.

Worth noting

116\frac{1}{16} is the chance of no tail at all.

Concept
At least one, through the complement
Typical time
120 s
Your time
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The rule this testsRandom variables
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