$A$ four-digit number is to be formed using the digits $1, 2, 3, 4, 5, 6, 7$ (no digit is repeated). What is the probability that the number formed is $> 4000$?

$A$ 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

Two cards are drawn without replacement from a well-shuffled pack. Find the probability that one of them is an ace of hearts.

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 $5$ red and $4$ green balls. If four balls are drawn at random,what is the probability that two balls are red and two balls are green?

If two numbers $a$ and $b$ are chosen from the set of integers $1$ to $39$,then the probability that those numbers satisfy the equation $7a - 9b = 0$ is