A bag contains $3$ white and $2$ black balls and another bag contains $2$ white and $4 $ black balls. A ball is picked up randomly. The probability of its being black is

A card is selected from a pack of $52$ cards. Calculate the probability that the card is an ace of spades.

Choose a number $n$ uniformly at random from the set $\{1,2, \ldots, 100\}$. Choose one of the first seven days of the year $2014$ at random and consider $n$ consecutive days starting from the chosen day. What is the probability that among the chosen $n$ days, the number of Sundays is different from the number of Mondays?

A number is chosen at random from the set $\{1,2,3, \ldots, 2000\}$. Let $p$ be the probability that the chosen number is a multiple of $3$ or a multiple of $7$ . Then the value of $500\ p$  is. . . . . . 

One card is drawn from a well shuffled deck of $52$ cards. If each outcome is equally likely, calculate the probability that the card will be not a black card.

In a single throw of two dice the probability of obtaining an odd number is