Question

. If A = {x : x is a multiple of 4} and B = {x: x is multiple of 5}, then A∩B consists of all multiples of :

Answer 1

i ) A = {x : x is a multiple of 4}

=> A = { 4,8,12,16,20, 24,28,32,36,40, ... }

ii ) B = {x: x is multiple of 5}

=> B = { 5,10,15,20,15,30, 35,40,45, ...}

$Now, A\cap B \\=\{ 4,8,12,16,20, 24,28,32,36,40, \cdot\cdot\cdot,\}\cap \{ 5,10,15,20,15,30, 35,40,45, \cdot\cdot\cdot\}$

$= \{ 20, 40, \cdot\cdot\cdot , \}$

$= \{ Multiple \: of \: 20 \}$

Therefore.,

$\red{ A\cap B } \green {= \{ Multiple \: of \: 20 \}}$

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