The solution of which equation is an irrational number ?  A) 1/x = 3/4

Correct option is (B) x² = 49/20

(A) \(\frac{1}{x}=\frac{3}{4}\) \(\Rightarrow\) \(x=\frac{1}{\frac{3}{4}}=\frac{4}{3}\) is a rational number.

(B) \(x^2=\frac{49}{20}\) \(\Rightarrow\) \(x=\sqrt{\frac{49}{20}}=\frac{7}{2\sqrt5}\) is an irrational number.

(C) \(\frac{1}{2}x+\frac{1}{5}=\frac{1}{3}\) \(\Rightarrow\) \(\frac x2=\frac13-\frac{1}{5}=\frac{2}{15}\) \(\Rightarrow x=\frac4{15}\) is a rational number.

(D) \(x^2=\frac{9}{16}\) \(\Rightarrow\) \(x=\sqrt{\frac{9}{16}}=\frac{\sqrt9}{\sqrt{16}}=\frac{3}{4}\) is a rational number.

Correct option is (B) x² = 49/20