A pair of dice is thrown and the sum of the numbers appearing on the dice is observed to be 7 . Find the probability that the number 5 has appeared on atleast one die.ORThe probability that $A$ hits the target is $\;\frac{1}{3}$ and the probability that $B$ hits it, is $\;\frac{2}{5}$. If both try to hit the target independently, find the probability that the target is hit.