The probability of a student passing any exam is 2/3. If the student takes three exams, what is the probability that he will not pass any of them?

Jc2004

4 years ago

i really dont understand why 1 was subtracted from 2\3......
can someone please expain??

Chuks612

9 years ago

The right answer is B.

P of pass=2/3

P of fail=1-2/3=1/3

The question says that he passes two of his tests and fails just one. Therefore, it's going to be...

P(pass,pass,fail) or P(pass,fail,pass) or P(fail,pass,pass)

=(2/3*2/3*1/3)+(2/3*1/3*2/3)+(1/3*2/3*2/3)....or changes to plus cuz its a mutually exclusive event.

=4/27+4/27+4/27

= 12/27 =4/9(3 can still divide the proper fraction)