From a pack of $52$ cards,two cards are drawn in succession one by one without replacement. The probability that both are aces is

$A$ and $B$ are independent events. Their probabilities are $3/10$ and $2/5$ respectively. What is the probability that exactly one of the events occurs?

$A$ person has undertaken a construction job. The probabilities are $0.65$ that there will be a strike,$0.80$ that the construction job will be completed on time if there is no strike,and $0.32$ that the construction job will be completed on time if there is a strike. Determine the probability that the construction job will be completed on time.

$A$ woman has $10$ keys,out of which only one opens a lock. She tries the keys one after another (keeping aside the failed ones) until she succeeds in opening the lock. What is the probability that the seventh key works?

Two cards are drawn from a pack of well-shuffled $52$ playing cards one by one without replacement. The probability that both cards are queens is:

$A$ purse contains $4$ copper and $3$ silver coins. $A$ second purse contains $6$ copper and $2$ silver coins. If a coin is drawn from any one of these two purses,what is the probability that it is a copper coin?