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A coin is tossed six times. What is the probability of getti

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A coin is tossed six times. What is the probability of getti [#permalink] New post 04 May 2018, 10:31
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A coin is tossed six times. What is the probability of getting at least four heads on the tosses?

A. \(\frac{1}{64}\)

B. \(\frac{3}{32}\)

C. \(\frac{15}{64}\)

D. \(\frac{11}{32}\)

E. \(\frac{90}{64}\)
[Reveal] Spoiler: OA

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Re: A coin is tossed six times. What is the probability of getti [#permalink] New post 05 May 2018, 11:15
Some one please explain this? I think I took the wrong route
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Re: A coin is tossed six times. What is the probability of getti [#permalink] New post 06 May 2018, 10:07
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The probability is = N. of desired outcomes/N. of possible outcomes.

Starting to calculate your denominator, we do have 6 tosses. Each one can give you Head or Tail : H or T.

For six times we do have \(2^6 = 64\)

Now, the denominator: at least four heads means 4 H, 5H or 6H.

To calculate 4 H we do use the combination formula \(6C2\) (because we do have four H and 2 T) so we do have 15 possible combinations

\(6C5\) we do have 6 combinations.

For \(6C6\) actually is 1

\(15+6+1=22\)

Our probability is \(\frac{22}{64}= \frac{11}{32}\) so the answer is D
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Re: A coin is tossed six times. What is the probability of getti   [#permalink] 06 May 2018, 10:07
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