Question

Find the cardinal number of the following set.

P = {x : x = 3n + 2, n ∈ W and x < 15}

Answer 1

W = {0, 1, 2, 3, …….}

if n = 0, x = 3(0) + 2 = 2

if n = 1, x = 3(1) + 2 = 5

if n = 2, x = 3(2) + 2 = 8

if n = 3, x = 3(3) + 2 = 11

if n = 4, x = 3(4) + 2 = 14

∴ P = {2, 5, 8, 11, 14}

n(P) = 5