Q.Find the probability of getting both red balls, when from a bag containing 5 red and 4 black balls, two balls are drawn, i) with replacement ii) without replacement.

For a random experiment whose outcomes are all equally likely (no outcome is preferred over any other), the classical definition assigns to an event $A$ the probability $P(A)=n(A)/n(S)$, the fraction of all outcomes that are favourable to $A$. This single ratio - favourable outcomes over total outcomes - is the computational engine of the whole chapter: once a sample space is built and the outcomes favouring an ev …