Q.Find the probability of getting D in the first place in all possible arrangements of each and every letter of the word DHYAN.

For any event $A$, $0\le P(A)\le1$.

By the axiomatic definition of probability, the probability of any event $A$ of the sample space satisfies $0\le P(A)\le1$. It cannot be negative and cannot exceed $1$. Option (b) is …

A non-leap February has $28$ days $= 4$ full weeks, so every day of the week appears exactly $4$ times; getting $5$ Mondays is impossible, probability $= 0$ — option (a).

GSEB Class-12 Statistics, Probability:

In a non-leap year, February has $28$ days.

$28 = 4 \times 7$

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The classical definition of probability is also known as the mathematical (a priori) definition.

Reasoning. The classical approach defines $P(A) = \dfrac{\text{favourable outcomes}}{\text{total equally likely outcomes}}$ purely by reasoning/counting, before any experiment. Hence it is called the mathematical or a prior …