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# If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4

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Senior RC Moderator
Joined: 02 Nov 2016
Posts: 4118
GPA: 3.39
If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4  [#permalink]

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31 Mar 2019, 08:28
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Difficulty:

5% (low)

Question Stats:

97% (00:48) correct 3% (02:50) wrong based on 30 sessions

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If $$= \frac{7}{x} + \frac{2}{y} = 7$$ and $$xy = 4$$, then $$7y + 2x =?$$

A. 28

B. 14

C. $$\frac{7}{4}$$

D. $$\frac{4}{7}$$

E. $$\frac{2}{7}$$

Source: McGraw-Hill's GMAT
Difficulty Level: 550

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Posts: 4009
Re: If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4  [#permalink]

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31 Mar 2019, 08:52
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Top Contributor
If $$\frac{7}{x} + \frac{2}{y} = 7$$ and $$xy = 4$$, then $$7y + 2x =?$$

A. 28

B. 14

C. $$\frac{7}{4}$$

D. $$\frac{4}{7}$$

E. $$\frac{2}{7}$$

Source: McGraw-Hill's GMAT

Given: $$\frac{7}{x} + \frac{2}{y} = 7$$

Multiply both sides by x to get: $$7 + \frac{2x}{y} = 7x$$

Multiply both sides by y to get: $$7y + 2x = 7xy$$

Since we're told that xy = 4, we can take the above equation and replace xy with 4 to get: $$7y + 2x = 7(4)$$

Simplify: $$7y + 2x = 28$$

Cheers,
Brent
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Posts: 5020
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4  [#permalink]

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31 Mar 2019, 10:17
If $$= \frac{7}{x} + \frac{2}{y} = 7$$ and $$xy = 4$$, then $$7y + 2x =?$$

A. 28

B. 14

C. $$\frac{7}{4}$$

D. $$\frac{4}{7}$$

E. $$\frac{2}{7}$$

Source: McGraw-Hill's GMAT

solve the eqn
m]= \frac{7}{x} + \frac{2}{y} = 7[/m]
7y+2x=7xy
xy=4 given
so 7x+2y= 28
IMO A
Senior RC Moderator
Joined: 02 Nov 2016
Posts: 4118
GPA: 3.39
Re: If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4  [#permalink]

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31 Mar 2019, 10:23
Don't worry dear, after approx 30 timers attempts GMAT Club timer's system automatically manage its difficulty level.

Thanks

Archit3110 wrote:
If $$= \frac{7}{x} + \frac{2}{y} = 7$$ and $$xy = 4$$, then $$7y + 2x =?$$

A. 28

B. 14

C. $$\frac{7}{4}$$

D. $$\frac{4}{7}$$

E. $$\frac{2}{7}$$

Source: McGraw-Hill's GMAT

solve the eqn
m]= \frac{7}{x} + \frac{2}{y} = 7[/m]
7y+2x=7xy
xy=4 given
so 7x+2y= 28
IMO A

_________________
GMAT Club Legend
Joined: 18 Aug 2017
Posts: 5020
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4  [#permalink]

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31 Mar 2019, 10:25
Don't worry dear, after approx 30 timers attempts GMAT Club timer's system automatically manage its difficulty level.

Thanks

Archit3110 wrote:
If $$= \frac{7}{x} + \frac{2}{y} = 7$$ and $$xy = 4$$, then $$7y + 2x =?$$

A. 28

B. 14

C. $$\frac{7}{4}$$

D. $$\frac{4}{7}$$

E. $$\frac{2}{7}$$

Source: McGraw-Hill's GMAT

solve the eqn
m]= \frac{7}{x} + \frac{2}{y} = 7[/m]
7y+2x=7xy
xy=4 given
so 7x+2y= 28
IMO A

ohh well thats a fun fact I wasnt aware of this... thanks for sharing..
Re: If = 7/x + 2/y = 7 and xy = 4, then 7y + 2x =? A. 28 B. 14 C. 7/4 D. 4   [#permalink] 31 Mar 2019, 10:25
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