A five-question quiz is taken in which the first and second questions have four answer choices, the third and fourth questions have three answer choices, and the last question has five answer choices. If a student randomly marks an answer for each question, what is the expected number of questions he will answer correctly?

Respuesta :

Answer:

1.37

Step-by-step explanation:

The student can give only 0.139 % answer correctly.

The first and second questions have four answer choices,

Probability of first and second question answer correctly is,

                [tex]P_{1}=\frac{1}{4}*\frac{1}{4} =\frac{1}{16}[/tex]

The third and fourth questions have three answer choices,

Probability of third and fourth question answer correctly is,

           [tex]P_{2}=\frac{1}{3} *\frac{1}{3}=\frac{1}{9}[/tex]

The last question has five answer choices.

Probability of fifth question answer correctly is,

              [tex]P_{3}=\frac{1}{5}[/tex]

The probability of corrected answer is,

        [tex]P=P_{1}*P_{2}*P_{3}\\\\P=\frac{1}{16} *\frac{1}{9}*\frac{1}{5}=\frac{1}{720}[/tex] = 0.139 %

Hence, The student  can give only 0.139 % answer correctly.

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