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MHT CET · Maths · Probability

Out of 100 people selected at random, 10 have common cold. If five persons selected at random from the group, then the probability that at most one person will have common cold is

  1. A \(0.9254\)
  2. B \(0.9185\)
  3. C \(0.9851\)
  4. D \(0.9245\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(0.9185\)

Step-by-step Solution

Detailed explanation

(C)
Let probability of having common cold \(\mathrm{p}=\frac{10}{100}=\frac{1}{10} \Rightarrow \mathrm{q}=\frac{9}{10}\) Here \(\mathrm{n}=5\), and \(\mathrm{x}=0,1\).
Hence required probability
\(\begin{array}{l}
={ }^{5} \mathrm{C}_{0}\left(\frac{1}{10}\right)^{0}\left(\frac{9}{10}\right)^{5}+{ }^{5} \mathrm{C}_{1}\left(\frac{1}{10}\right)^{1}\left(\frac{9}{10}\right)^{4} \\
=\left(\frac{9}{10}\right)^{5}+\frac{5(9)^{4}}{(10)^{5}}=\frac{\left(9^{4}\right)[9+5]}{(10)^{5}}=\frac{81 \times 81 \times 14}{10^{5}}=0.9185
\end{array}\)