A student knows 30 of 35 answers that should be learned for the exam. There two questions in a question card.what is the probability that student doesn't know all two answers?
The total number of combination for preparing a question card with 2 questions out of 35 questions is given by 35C2
The total number of combinations for not knowing both the questions from a question card is given by 5C2 (since there are 5 questions (35-30=5) that a student does not know out of 35 questions)
Hence the probability that a student does not know both the questions in a question card is given by,
The probability that student doesn't know all two answers = 0.0168
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