If $20 \%$ of the bolts produced by a machine are defective, then the probability that out of $4$ bolts chosen at random, less than $2$ bolts will be defective, is

$A$ radar system can detect an enemy plane in one out of $10$ consecutive scans. The probability that it cannot detect an enemy plane at least two times in four consecutive scans is:

$A$ fair coin is tossed a fixed number of times. If the probability of getting exactly $3$ heads equals the probability of getting exactly $5$ heads, then the probability of getting exactly one head is

Assuming that for a husband-wife couple,the chances of their child being a boy or a girl are the same,the probability of their two children being a boy and a girl is:

The probability of a man hitting a target is $\frac{1}{10}$. The least number of shots required,so that the probability of his hitting the target at least once is greater than $\frac{1}{4}$,is

$A$ fair coin is tossed a fixed number of times. If the probability of getting five heads is equal to that of getting seven heads, then the probability of getting four heads is