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CDS Model Paper 1 Mathematics

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Question : 39 of 100

Marks: +1, -0

If

\frac{5x-7y+10}{1}=\frac{3x+2y+1}{8}=\frac{11x+4y-10}{9}

x+y

equal to?

1
2
3
$-3$

Solution:

Given,

\frac{5x-7y+10}{1}=\frac{3x+2y+1}{8}=\frac{11x+4y-10}{9}

=\frac{(5x+10-7y)+(3x+2y+1)-(11x+4y-10)}{(1+8)-9}

=\frac{-3x-9y+21}{0}

⇒

x+3y=7

...(i)

On taking first two terms,

8(5x-7y+10)=3x+2y+1

37x-58y+79=0

....(ii)

From equation (i), on putting the value of

x

in equation (ii), we get

37(7-3y)-58y+79=0

⇒

259-111y-58y+79=0

⇒

169y=338

⇒

y=2

From equation (i),

x=7-3(2)=1

∴

x+y=1+2=3

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