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Question: Answered & Verified by Expert
A salesman has a $70 \%$ chance to sell a product to any customer. The behaviour of successive customers is independent. If two customers $\mathrm{A}$ and $\mathrm{B}$ enter, what is the probability that the salesman will sell the product to customer A or B?
MathematicsProbabilityNDANDA 2016 (Phase 2)
Options:
  • A $0.98$
  • B $0.91$
  • C $0.70$
  • D $0.49$
Solution:
1206 Upvotes Verified Answer
The correct answer is: $0.91$
$\quad P(A)=\frac{70}{100}=\frac{7}{10}=P(B)$
$A$ and $B$ are independent.
$\begin{aligned} \Rightarrow P(A \cap B) &=P(A) P(B) \\ \Rightarrow P(A \cup B) &=P(A)+P(B)-P(A \cap B) \\ &=\frac{7}{10}+\frac{7}{10}-\frac{7}{10} \times \frac{7}{10}=0.91 \end{aligned}$

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