Question

In an examination a candidate has to pass in each of four subject . In how many ways can he fails?

Answer 1

No. of ways in which one can pass or fail in the examination $\left(m\right)=2^4=16$24=16

To pass one has to pass in all the subjects $\left(n\right)=1way$

Hence, the no. of ways in which one can fail $=(m-n)$

$=16-1$

$=15ways$