Six boys and six girls sit in a row randomly. What is the probability that the six girls sit together?

$A$ bag $X$ contains $2$ white and $3$ black balls and another bag $Y$ contains $4$ white and $2$ black balls. One bag is selected at random and a ball is drawn from it. Then the probability for the ball chosen to be white is

$A$ fair coin is tossed repeatedly. If a tail appears on the first four tosses,then the probability of a head appearing on the fifth toss equals:

Three letters are to be sent to different persons,and addresses on the three envelopes are also written. Without looking at the addresses,the probability that all the letters go into the right envelope is equal to

The probability that a man will be alive $25$ years hence is $0.3$ and the probability that his wife will be alive $25$ years hence is $0.4$. Find the probability that $25$ years hence,only the man will be alive.

$A$ card is drawn from a pack of $52$ cards. Find the probability of getting a spade,an ace,or a red card.