$A$ box contains $10$ good articles and $6$ with defects. One article is chosen at random. What is the probability that it is either good or has a defect?

For two events $A$ and $B$,if $P(A) = P(A|B) = 1/4$ and $P(B|A) = 1/2$,then

Find the probability that in a random arrangement of the letters of the word $DAUGHTER$,the letter $D$ occupies the first place.

In a simultaneous toss of $2$ coins,find the probability of getting exactly $1$ tail.

If $P(A_1 \cup A_2) = 1 - P(A_1^c) P(A_2^c)$,where $c$ stands for complement,then the events $A_1$ and $A_2$ are

$A$ locker can be opened by dialing a fixed three-digit code (between $000$ and $999$). $A$ stranger who does not know the code tries to open the locker by dialing three digits at random. The probability that the stranger succeeds at the $k^{th}$ trial is