Chapter 7 - Section 7.1 - An Introduction to Discrete Probability - Exercises - Page 451: 16

Probability = $\frac{5148}{2398960}$ $\approx$ 0.002146

Number of ways to select 5 cards from deck = $C$(52,5) = 2598960 For a flush we need 5 cards of the same suit, It can be any of the 4 suit - It can be done in $C$(13,5)$\times$4 = 5148 Probability = $\frac{5148}{2398960}$ $\approx$ 0.002146