Three persons $A, B$,and $C$ are to speak at a function. If they speak in a random order,what is the probability that $A$ speaks before $B$ and $B$ speaks before $C$?

$A$ bag contains $9$ identical black balls numbered $1$ to $9$ and $4$ identical white balls numbered $1$ to $4$. If $3$ balls are drawn at a time randomly from that bag,then the probability of getting at least one white ball is

In a certain lottery,$10,000$ tickets are sold and $10$ equal prizes are awarded. What is the probability of not getting a prize if you buy $2$ tickets?

$A$ bag contains $10$ identical pens,of which $4$ are red and $6$ are blue. $3$ pens are taken out at random one after another. Find the probability that all $3$ are blue.

Out of $30$ consecutive numbers,$2$ are chosen at random. The probability that their sum is odd,is

Twenty tickets are marked with the numbers $1, 2, \dots, 20$. If three tickets are drawn at random,what is the probability that the tickets marked $7$ and $11$ are among them?