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NDA 2010
Exam
NDA
Year
2010
Subject
Mathematics
Chapter
Probability

NDA 2010 · Mathematics · Probability

In tossing three coins at a time, what is the probability of...

In tossing three coins at a time, what is the probability of getting at most one head?

Options

  1. A38\frac{3}{8}
  2. B78\frac{7}{8}
  3. C12\frac{1}{2}
  4. D18\frac{1}{8}

Correct answer

C. 12\frac{1}{2}

Step-by-step solution

P=P(x=0)+P(x=1)=3C0(12)3(12)0+3C1(12)2(12)1=1×18+3×18=12\begin{aligned} & \mathrm{P}=\mathrm{P}(x=0)+\mathrm{P}(x=1) \\ & ={ }^3 C_0\left(\frac{1}{2}\right)^3\left(\frac{1}{2}\right)^0+{ }^3 C_1\left(\frac{1}{2}\right)^2\left(\frac{1}{2}\right)^1 \\ & =1 \times \frac{1}{8}+3 \times \frac{1}{8}=\frac{1}{2}\end{aligned}
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