$A$ bag contains $3$ black and $4$ white balls. Two balls are drawn one by one at random without replacement. The probability that the second drawn ball is white,is

One card is drawn from each of two ordinary packs of $52$ cards. The probability that at least one of them is an ace of heart,is

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

$A$ bag contains $13$ white and $7$ black balls. $2$ balls are drawn at random. What is the probability that they are of the same colour?

$A$ 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 numbers is:

$A$ bag contains $4$ white balls and $2$ black balls. Another bag contains $3$ white balls and $5$ black balls. If one ball is drawn from each bag,then the probability that both the balls are black,is