Question 86

If $$\frac{11-13x}{x}+\frac{11-13y}{y}+\frac{11-13z}{z}=5$$, then what is value of $$\frac{1}{x}+\frac{1}{y}+\frac{1}{z}$$ ?

Solution

Given : $$\frac{11-13x}{x}+\frac{11-13y}{y}+\frac{11-13z}{z}=5$$

Let $$\frac{11-13x}{x}=\frac{11-13y}{y}=\frac{11-13z}{z}=k$$

=> $$k+k+k=5$$

=> $$k=\frac{5}{3}$$

=> $$\frac{11-13x}{x}=\frac{5}{3}$$

=> $$33-39x=5x$$

=> $$39x+5x=44x=33$$

=> $$x=\frac{33}{44}=\frac{3}{4}$$ -------(i)

Similarly, $$y=z=\frac{3}{4}$$ --------(ii)

To find : $$\frac{1}{x}+\frac{1}{y}+\frac{1}{z}$$

= $$\frac{4}{3}+\frac{4}{3}+\frac{4}{3}$$

= $$\frac{12}{3}=4$$

=> Ans - (D)


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