An urn contains $9$ red,$7$ white and $4$ black balls. If two balls are drawn at random,then the probability that one is white and the other is red is

$A$ drawer contains $50$ bolts and $150$ nuts. Half of the bolts and half of the nuts are rusted. If $1$ item is chosen at random,what is the probability that it is rusted or is a bolt?

Fifteen persons,including $A$ and $B$,sit down at random at a round table. The probability that there are $4$ persons between $A$ and $B$ is

Suppose that a die (with faces marked $1$ to $6$) is loaded in such a manner that for $K = 1, 2, 3, 4, 5, 6$,the probability of the face marked $K$ turning up when the die is tossed is proportional to $K$. The probability of the event that the outcome of a toss of the die will be an even number is equal to

In a college,$25\%$ of the boys and $10\%$ of the girls offer Mathematics. The girls constitute $60\%$ of the total number of students. If a student is selected at random and is found to be studying Mathematics,the probability that the student is a girl,is

Out of $40$ consecutive natural numbers,two are chosen at random. The probability that the sum of the numbers is odd is: