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What is the average of x and y?

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What is the average of x and y? [#permalink]

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New post 04 Nov 2015, 06:27
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Question Stats:

77% (00:20) correct 23% (00:21) wrong based on 149 sessions

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What is the average of x and y?

1. x + y = 20
2. 2x + 4y = 54
[Reveal] Spoiler: OA

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Re: What is the average of x and y? [#permalink]

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New post 04 Nov 2015, 08:23
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shyind wrote:
What is the average of x and y?

1. x + y = 20
2. 2x + 4y = 54


Target question: What is the average of x and y?
Average of x and y = (x + y)/2
So, to find the average, we need only find the value of x+y

Statement 1: x + y = 20
Perfect!
So, average = (x + y)/2
= 20/2
= 10
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: 2x + 4y = 54
Divide both sides by 2 to get: x + 2y = 27
This doesn't help, because we need the value of x + y.
To understand why this statement is not sufficient, let's test some values. There are several values of x and y that satisfy statement 2. Here are two:
Case a: x = 1 and y = 13, in which case the average of x and y = (1+13)/2 = 7
Case b: x = 9 and y = 9, in which case the average of x and y = (9+9)/2 = 9[/color]
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer = A

Cheers,
Brent
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Brent Hanneson – Founder of gmatprepnow.com

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Re: What is the average of x and y? [#permalink]

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New post 04 Nov 2015, 09:06
shyind wrote:
What is the average of x and y?

1. x + y = 20
2. 2x + 4y = 54


Target question: What is the average of x and y?
Average of x and y = (x + y)/2
So, to find the average, we need only find the value of x+y

Statement 1: x + y = 20
Perfect!
So, average = (x + y)/2
= 20/2
= 10
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: 2x + 4y = 54
Divide both sides by 2 to get: x + 2y = 27
This doesn't help, because we need the value of x + y.
To understand why this statement is not sufficient, let's test some values. There are several values of x and y that satisfy statement 2. Here are two:
Case a: x = 1 and y = 13, in which case the average of x and y = (1+13)/2 = 7
Case b: x = 9 and y = 9, in which case the average of x and y = (9+9)/2 = 9
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer = A

Cheers,
Brent
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Brent Hanneson – Founder of gmatprepnow.com

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Re: What is the average of x and y? [#permalink]

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New post 08 Jul 2017, 14:50
shyind wrote:
What is the average of x and y?

1. x + y = 20
2. 2x + 4y = 54



\(Average = \frac{Sum}{Count}\)

So in order to find the average of x and y we will need the sum of \(x + y\)

\((1) x + y = 20\)
As this equation directly gives us the value of x + y which is what we are looking for, we will be able to find average.

\(Average = \frac{x + y}{2}\)

\(Average = \frac{20}{2}\)

\(Average = 10\)


Hence, (1) ===== is SUFFICIENT



\((2) 2x + 4y = 54\)

From this equation we will not be able to determine the value of x + y and hence this equation is not sufficient.

Hence, (2) ===== is NOT SUFFICIENT

Hence, Answer is A
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Re: What is the average of x and y?   [#permalink] 08 Jul 2017, 14:50
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