If the ratio x: y:z is 3:5:7, what is the value of z : GMAT Data Sufficiency (DS)
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# If the ratio x: y:z is 3:5:7, what is the value of z

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If the ratio x: y:z is 3:5:7, what is the value of z [#permalink]

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29 Nov 2012, 08:56
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If the ratio x: y:z is 3:5:7, what is the value of z?

(1) The average (arithmetic mean) of x, y, and z is 25.
(2) The value of x is 15.
[Reveal] Spoiler: OA

Last edited by Bunuel on 19 Mar 2015, 04:38, edited 2 times in total.
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Re: If the ratio x: y:z is 3:5:7, what is the value of z [#permalink]

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29 Nov 2012, 09:01
ritumaheshwari02 wrote:
If the ratio x: y:z is 3:5:7, what is the value of z?

(1) The average (arithmetic mean) of x, y, and z is 25.
(2) The value of x is 15.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

x:y:z = 3:5:7
means x=3k, y=5k, z=7k where k is the common value in all the three numbers.

STAT1
(x+y+z)/3 = 25
x+y+z = 75
=> 3k + 5k+ 7k = 75
15k = 75
k = 5
z = 7k = 35
SUFFICIENT

STAT2
x= 15
=> 3k = 15
=> k =5
=> z = 7k = 7*5 = 35
SUFFICIENT

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Re: If the ratio x: y:z is 3:5:7, what is the value of z [#permalink]

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17 Mar 2015, 05:06
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Re: If the ratio x: y:z is 3:5:7, what is the value of z [#permalink]

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18 Mar 2015, 19:04
Hi All,

With the given ratio, we know that X is a multiple of 3, Y is an equivalent multiple of 5 and Z is an equivalent multiple of 7. By extension, the sum of those 3 terms is a multiple of 15

For example, we could have X=3, Y=5 and Z=7 (and the sum = 15) or X=6, Y=10, Z=14 (and the sum = 30)

We're asked for the value of Z .

Fact 1: The average (arithmetic mean) of x, y, and z is 25.

Since the average of the 3 terms is 25, the SUM of the three terms is 75.

75 is a 5 times 15, so we can calculate the value of all 3 variables:

X = 3(5) = 15
Y = 5(5) = 25
Z = 7(5) = 35
Fact 1 is SUFFICIENT

Fact 2: The value of x is 15.

Since X = 15, we can figure out the "multiple of 3" that we're dealing with. 3(5) = 15, so we have to multiply the Y and the Z by 5 also.

Y = 5(5) = 25
Z = 7(5) = 35
Fact 2 is SUFFICIENT

[Reveal] Spoiler:
D

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Re: If the ratio x: y:z is 3:5:7, what is the value of z [#permalink]

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18 Sep 2016, 21:47
Hello from the GMAT Club BumpBot!

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Re: If the ratio x: y:z is 3:5:7, what is the value of z   [#permalink] 18 Sep 2016, 21:47
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