CFA level 1 Quant Discrete uniform distribution

CFA Level I Quant
#1

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can someone please help me in understanding the 2nd question i.e. finding P(4 <= X <= 6) using 2nd logic i.e. calculating the probability as the difference between two values of the cdf: F(6)-F(3)

F(6) is understood but why are taking F(3) and not F(4) here?

Thanks!

#2

F(4) = P(X ≤ 4).

If you subtract F(4), you lose P(X = 4), which you want to keep.

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