CMAT 2015 Solved Question Paper

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Question : 20 of 100

Marks: +1, -0

If

(1/x + 1/y)

varies inversely as (x + y) and k is a constant of proportionality, then

(x^2 +y^2)/(xy)

is

k + 1
k
k - 2
k - 1

Solution:

(c) Given,

1/x + 1/y∝ 1/{x+y}

⇒

1/x + 1/y=k/{x+y}

⇒

{x+y}/{xy} = k/{x+y}

⇒

(x+y)^2

= xy⋅k
⇒

{x^2+y^2+2xy}/{xy}

= k
⇒

{x^2+y^2}/{xy}

+ 2 = k
∴

{x^2+y^2}/{xy}

= k - 2

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