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Value of y^3

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Value of y^3

by raleigh » Fri Jun 19, 2009 5:13 pm
It's one of those problems that can trick you if you rush. I got this in the MGMAT question bank. I thought it was pretty good so I'm sharing it.

If x is not equal to y and if y=x^(1/2), what is the value of y^3 ?

(1) x = y^x

(2) x^3 = 8

OA D
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Source: — Data Sufficiency |
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by ssmiles08 » Fri Jun 19, 2009 5:50 pm
I figured both x and y are positive b/c sqrt(+) = +

Choice 1 tells us that

x = y^x

we know that y=x^(1/2); squaring both sides: y^2 = x

substitute for x: y^x = y^2

so x = 2

we know one of the values, we can easily figure out value of y^3.

Choice 2 tells us that x^3 = 8

we can manipulate the equation like: [y]^6=[x^(1/2)]^6

y^6 = x^3

y^6 = 8

(y^6)^1/2 = y^3 = 8^(1/2)

(D)
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