The sum of two positive numbers is $100$. The probability that their product is greater than $1000$ is

A bag contains $19$ tickets numbered from $1$ to $19$. A ticket is drawn and then another ticket is drawn without replacement. The probability that both the tickets will show even number, is

The probability that an event will fail to happen is $0.05$. The probability that the event will take place on $4$ consecutive occasions is

An experiment consists of recording boy-girl composition of families with $2$ children. What is the sample space if we are interested in the number of girls in the family?

Three letters are dictated to three persons and an envelope is addressed to each of them, the letters are inserted into the envelopes at random so that each envelope contains exactly one letter. Find the probability that at least one letter is in its proper envelope.

There are $10$ pairs of shoes in a cupboard from which $4$ shoes are picked at random. The probability that there is at least one pair, is