Question

a multiple choice test has 9 questions Each of which has 4 possible answers, only one of which is correct. If Judy, I forgot to study for the test, gas is on all the questions, what is the probability that she will answer exactly three questions correctly

Answer 1

Given

9 questions

4 possible answers

only one of which is correct

what is the probability that she will answer exactly three questions correctly​?

Procedure

n=9

p=1/4=25%

`P\mleft(x=3\mright)=9C3*\mleft(1/4\mright)^3\cdot\mleft(3/4\mright)^6=`
`\begin{gathered} P(x=3)=84\cdot(1)/(64)\cdot0.178 \\ P(x=3)=0.2336 \end{gathered}`

The answer is 23.36% that she will answer exactly three questions correctly​