If an = {ax : x ∈ N}, the

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Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Relations and Functions

Question:

If an = {ax : x ∈ N}, then 3N ∩ 7N =

Options:

21N

Correct Answer:

21N

Explanation:

We have 3N = {3x : x ∈ N} = {3, 6, 9, 12,…}

And 7N = {7x : x ∈ N} = {7, 14, 21, 28, 35, 42…}

Hence 3N ∩ 7N = {21, 42, 63, ….} = {21x : x ∈ N} = 21N

Hence (4) is the correct answer.