Question
If n is a natural number, then $\sqrt{\text{n}}$ is:

Answer

  1. sometimes a natural number and sometimes an irrational number.
    Solution:
  1. Is incorrect, because $\sqrt{\text{n}}$ can not be always a natural number
    i.e. if $\text{n}=2, \ \sqrt{\text{n}}=\sqrt{2}$ (not a natural no.)
  1. Is incorrect, similiarly, if n = 2, 5, …. Or any odd no. or not perfect square, $\sqrt{\text{n}}=\sqrt{2},\sqrt{5},\sqrt{7}$ are Non-terminating and non-repeating, So irrational in nature, So, not always a rational number.
  2. Is also incorrect, $\sqrt{\text{n}}$ can aslo be rational or say a natural number. If n = 4, 9, 16... or any perfect square number then $\sqrt{\text{n}}=2,3,4...$ natural numbers.
  3. Is fully correct because if n is any odd number or non-perfect square number then $\sqrt{\text{n}}$ would be irrational, but if n is a perfect square number $\sqrt{\text{n}}$ then will be a natural number.
    If n = 2, 3, 5, 8 ... $\sqrt{\text{n}}=\sqrt{2},\sqrt{3},\sqrt{8}...$ (irrational)
    If n = 4, 9, 16 ... = 2, 3, 4 ... (Natural number)
    So, correct option is (d).

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