Probability 67264

The teacher has 20 questions, from which the student chooses two on the exam. The student learned 10 questions well, 6 partially, and 4 not at all. What is the probability that he will get both questions he knows well?

Correct answer:

p =  0.2368

Step-by-step explanation:

$$\begin{gathered} a=10 \\ b=6 \\ c=4 \\ n=a+b+c=10+6+4=20 \\ p=\frac{a}{n}\cdot \frac{a-1}{n-1}=\frac{10}{20}\cdot \frac{10-1}{20-1}=\frac{9}{38}=0.2368 \end{gathered}$$

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