Probability
Grade 12

Question:

<p>There are 4 defective items in a lot of 10 items. If 5 items are selected at random, the probability that the selected items contain at most 1 defective item is</p>
A
B
C
D

Step-by-Step Solution

Key Concept: At most 1 defective = 0 defective + exactly 1 defective. Use hypergeometric counting.
<p>Total: \(\binom{10}{5} = 252\).</p><p>\(P(0\text{ defective}) = \dfrac{\binom{4}{0}\binom{6}{5}}{252} = \dfrac{6}{252}\)</p><p>\(P(1\text{ defective}) = \dfrac{\binom{4}{1}\binom{6}{4}}{252} = \dfrac{4 \times 15}{252} = \dfrac{60}{252}\)</p><p>\(P(\leq 1) = \dfrac{6 + 60}{252} = \dfrac{66}{252} = \dfrac{11}{42}\)</p>
Correct Answer: C

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