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  • A multiple choice examination has 5 question .Each question has three alternative answers of which exactly one is correct .The probability that a student will get 4 or more correct answers just by

A multiple choice examination has 5 question .Each question has three alternative answers of which exactly one is correct .The probability that a student will get 4 or more correct answers just by guessing is :

Option: 1

\frac{10}{3^{5}}


Option: 2

\frac{17}{3^{5}}


Option: 3

\frac{13}{3^{5}}


Option: 4

\frac{11}{3^{5}}


Answers (1)

best_answer

As learnt

Binomial Distribution -

Let E be an event and p+q = 1 then

X :          0                         1                            2         ..................     n

P(x):      qn                   {^n}c_1\cdot p^{1}q^{n-1}           {^n}c_2\cdot p^{2}q^{n-2}            pn

-

 

 

Number of ways of attempting=35

P\left ( X\geq 4 \right )\Rightarrow P(X=4)+P(X=5)

                   \Rightarrow \: ^{5}\textrm{C}_{4}\left ( \frac{1}{3} \right )^{4}\left ( \frac{2}{3} \right )+ \: ^{5}\textrm{C}_{5}\left ( \frac{1}{3} \right )^{5}

                  \Rightarrow \frac{11}{3^{5}}

Posted by

Ritika Kankaria

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