There are 30 students in the group. The marks for the control test were the following: 8 students received “excellent” marks, 12 students - “good” marks, 8 students – “satisfactory”. What is the probability that 3 students invited for answer have “good” marks?
Given:
n=30
number of students with good marks = 12
when r items are chosen from n items , use combination formula :
"nc_{r} == \\frac{n!}{r!(n-r)!}"
P(three students invites for answer have "good marks")= "\\frac{12C_{3}}{30C_{3}}" = "\\frac{220}{4060}= 0.0542"
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