The ratio of the number of boys to the number of girls in a class is $1: 2.$ It is known that the probability of a boy and girl getting a $I^{st}$ division are $0.25$ and $0.28$ respectively. Find the probability that a student chosen at random will get first division.

A box contains $2$ gold and $3$ silver coins. Another box contains $3$ gold and $3$ silver coins. A box is chosen at random, and a coin is drawn from it. If the selected coin is a gold coin, find the probability that it was drawn from the second box.

Two dice are rolled once. Find the probability that

$\left(i\right)$ The numbers on two dice are different.

$\left(ii\right)$ The total of numbers on the two dice at least $4$.