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 .........

Two balanced dice are rolled. Find the probability that the sum of numbers on two dice is odd.

Two dice are thrown at the same time. Determine the probability that the difference of the numbers on the two dice is $2$.

The probability of getting two heads in the experiment of tossing an unbiased coin twice is .........

Two dice,one blue and one grey,are thrown at the same time. Write down all the possible outcomes. What is the probability that the sum of the two numbers appearing on the top of the dice is
$(i)$ $8 ?$
$(ii)$ $13 ?$
$(iii)$ less than or equal to $12 ?$

Harpreet tosses two different coins simultaneously (say,one is of $Rs. 1$ and other of $Rs. 2$). What is the probability that she gets at least one head?