In a box,there are $2$ red,$3$ black,and $4$ white balls. If three balls are drawn together,what is the probability that the balls drawn are of the same colour?

If a number of two digits is formed with the digits $2, 3, 5, 7, 9$ without repetition of digits,what is the probability that the number formed is $35$?

$A$ 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

Two persons each make a single throw with a die. The probability they get equal value is ${p_1}$. Four persons each make a single throw and the probability of three being equal is ${p_2}$,then:

In an entrance test,there are multiple-choice questions. There are four possible answers to each question,of which one is correct. The probability that a student knows the answer to a question is $90\%$. If he gets the correct answer to a question,then the probability that he was guessing is:

What is the probability of getting a sum $9$ from two throws of a dice?