A lot of 100 watches is known to have 10 defective watches. If 8 watches are selected (one by one with replacement) at random, then what is the probability that there will be atleast one defective watch ?

Explanation

Probability of defective watch from a lot of 100 watches=`10/100=1/10`
`thereforep=1//10,q=9/10,n=8and rge1`
`thereforeP(rge1)=1-P(r=0)=1-""^(8)C_(0)(1/10)^(0)(9/10)^(8-0)`
`=1-(8!)/(0!8!)cdot(9/10)^(8)=1-(9/10)^(8)`