There are chits numbered $1$ to $20$ in a box. One chit is drawn at random. Find the probability that the number on the chit is an odd number.

The probability of a non-leap year having $53$ Fridays is $\ldots \ldots \ldots$

In a packet containing $400$ screws,$120$ screws are defective. $A$ screw is picked up randomly from the packet. Then,the probability that the screw picked up is non-defective is .........

$A$ bag contains $24$ balls of which $x$ are red,$2x$ are white,and $3x$ are blue. $A$ ball is selected at random. What is the probability that it is:
$(i)$ not red?
$(ii)$ white?

An unbiased coin is tossed thrice. The probability of receiving two heads is ..........

$12$ defective ballpens are mixed with $132$ non-defective ballpens. They all look alike. $A$ ballpen is selected at random from that lot. Find the probability that a defective ballpen is selected.