GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 17 Oct 2019, 08:34

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# If 4x/7y = 1, then what is the value of 3x + 5y ?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 58401
If 4x/7y = 1, then what is the value of 3x + 5y ?  [#permalink]

### Show Tags

31 Oct 2017, 23:02
00:00

Difficulty:

25% (medium)

Question Stats:

77% (01:16) correct 23% (01:13) wrong based on 96 sessions

### HideShow timer Statistics

If $$\frac{4x}{7y} = 1$$, then what is the value of 3x + 5y ?

(1) x + 4y = 23

(2) y^3 = 64

_________________
Current Student
Joined: 18 Aug 2016
Posts: 606
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
Re: If 4x/7y = 1, then what is the value of 3x + 5y ?  [#permalink]

### Show Tags

01 Nov 2017, 00:28
1
Bunuel wrote:
If 4x/7y = 1, then what is the value of 3x + 5y ?

(1) x + 4y = 23

(2) y^3 = 64

x = 7y/4

(1) 7y/4 + 4y = 23
23y = 23*4
y=4
then x = 7
3x +5y = 41..sufficient

(2) y = 4
then x = 7
3x +5y = 41..sufficient

D
_________________
We must try to achieve the best within us

Thanks
Luckisnoexcuse
Senior Manager
Joined: 07 Jul 2012
Posts: 367
Location: India
Concentration: Finance, Accounting
GPA: 3.5
Re: If 4x/7y = 1, then what is the value of 3x + 5y ?  [#permalink]

### Show Tags

01 Nov 2017, 19:35
$$\frac{4x}{7y}$$=1; x=$$\frac{7y}{4}$$

Put this value in (1)

$$\frac{7y}{4}$$+4y=23

$$\frac{7y+16y}{4}$$=23

y=4, then x=7

3x+5y= 3(7)+5(4)= 41 [Suff]

(2) $$y^3$$=64; y=4, then x=7

3x+5y= 3(7)+5(4)= 41 [Suff]

_________________
Kindly hit kudos if my post helps!
Manager
Joined: 25 Jul 2017
Posts: 55
Re: If 4x/7y = 1, then what is the value of 3x + 5y ?  [#permalink]

### Show Tags

01 Nov 2017, 20:43
Since 4x/7y=1 => 4x-7y = 0 (*)
1/ From 1 and from (*), we can find y = 4, x=7 => 3x+5y = 41 => Suff
2/ From 2 => y = 4 => x=7 =>3x+5y = 41 => Suff

Please hit kudos if it helps.
Manager
Joined: 11 Feb 2013
Posts: 149
GMAT 1: 490 Q44 V15
GMAT 2: 690 Q47 V38
GPA: 3.05
WE: Analyst (Commercial Banking)
If 4x/7y = 1, then what is the value of 3x + 5y ?  [#permalink]

### Show Tags

27 Mar 2019, 10:39
In this DS, No need to calculate values.

It's required to keep in mind that values of two unknown variriables can easily be found from two different equations with the condition that TWO EQUATIONS ARE NOT THE SAME EQUATION.

How to find out whether two equations are the same or different:
(1) X+2y =7 & (2)7x +14y=49
Here, (since 7x is 7 times x) if I multiply each variables of EQUATION 1 by 7, equation 1 will become exactly the same thing written in equation 2.

(1) X+2y =7 & (2)7x +8y=41
Here, (since 7x is 7 times x) if I multiply each variables of EQUATION 1 by 7, equation 1 will BE DIFFERENT FROM equation 2.

Posted from my mobile device
Manager
Joined: 11 Feb 2013
Posts: 149
GMAT 1: 490 Q44 V15
GMAT 2: 690 Q47 V38
GPA: 3.05
WE: Analyst (Commercial Banking)
Re: If 4x/7y = 1, then what is the value of 3x + 5y ?  [#permalink]

### Show Tags

27 Mar 2019, 10:54
STATEMENT 1: SUFFICIENT
Prompt says:
4x=7y
Or, 4x-7y=0....(1)
Statement 1: x+4y=23....(2)
Here, (1)TWO EQUATIONS & TWO VARIABLES
(2) BOTH EQUATIONS ARE THE SAME EQUATION.
So, I can easily find out the individual value of x and y.

If I have individual value of x and y, I can easily figure out anything with unknown variriable of x and y.
Thus, I can easily find out the value of 3x +5y.

STATEMENT 2:
Y= 4
[NB: ODD POWER DOESN'T CHANGE THE POSITIVE/NEGATIVE NATURE OF INPUT (BASE) AND OUTPUT (RESULT)]
Now the prompt (4x=7y) becomes (4x=7*4) "ONE EQUATION WITH ONE UNKNOWN VARIRIABLE" from which the value of unknown variriable can be found without calculation.

Now, I have individual value of x and y. So, I can easily figure out anything with unknown variriable of x and y.
Thus, I can easily find out the value of 3x +5y.

So. THERE IS NO NEED TO CALCULATION.

Posted from my mobile device
Re: If 4x/7y = 1, then what is the value of 3x + 5y ?   [#permalink] 27 Mar 2019, 10:54
Display posts from previous: Sort by