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

Final Answer:

GMAT assassins aren't born, they're made,

Rich

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http://www.empowergmat.com

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