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OG 13 -120
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A
B
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D
E
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The other way to solve this
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hemant_rajput
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Why you need another way? The way mentioned in the explanation is the easiest and quickest way to solve the given question. Solution doesn't even involve any calculation.[email protected] wrote:The other way to solve this
I'm no expert, just trying to work on my skills. If I've made any mistakes please bear with me.
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GMATGuruNY
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I would recommend straight algebra:If s>0 and √(r/s) = s, what is r in terms of s?
A) 1/s
B) √s
C) s√s
D) s³
E) s² - s
( √(r/s) )² = s²
r/s = s²
r = s³.
The correct answer is D.
An alternate approach is to plug in an easy value for s and solve for r.
If s=2, we get:
√(r/2) = 2.
Since √4 = 2, the value under the square root -- r/2 -- must be equal to 4:
r/2 = 4.
r = 8. This is our target.
Now we plug s=2 into the answer choices to see which yields our target of 8.
Only D works:
s³ = 2³ = 8.
For this problem, algebra seems easier and more efficient.
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Brent@GMATPrepNow
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Let's test some values that satisfy the given equation √(r/s) = sIf s > 0 and √(r/s) = s, what is r in terms of s ?
(A) 1/s
(B) √s
(C) s√s
(D) s^3
(E) s^2 - s
For example, r = 125 and s = 5 satisfies the equation √(r/s) = s
What is r in terms of s ?
Check the answer choices to see which one yields 125 when s = 5
(A) 1/5 ≠125 ELIMINATE
(B) √5 ≠125 ELIMINATE
(C) 5√5 ≠125 ELIMINATE
(D) 5^3 = 125 KEEP!!
(E) 5^2 - 5 ≠125 ELIMINATE
Answer: D
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Matt@VeritasPrep
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Brent, resurrecting threads! A GMAT expert and a necromancer ... 
Another way to do this one:
√(r/s) = s
square both sides:
r/s = s * s
multiply both sides by s:
r = s * s * s
Another way to do this one:
√(r/s) = s
square both sides:
r/s = s * s
multiply both sides by s:
r = s * s * s
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Hi All,
We’re told that S > 0 and root(R/S) = S. We’re asked for the value of R in terms of S.
Typically, when the phrase “in terms of” appears in a question, an Algebraic approach is required. However, this question can be solved rather easily by TESTing VALUES.
IF… S = 2, then root(R/S) = 2… meaning that R/2 has to equal 4. This means that R = 8… so we’re looking for an answer that equals 8 when S = 2. The answers are simple enough that you should be able to find the correct answer in a matter of seconds…
Final Answer: D
GMAT Assassins aren’t born, they’re made,
Rich
We’re told that S > 0 and root(R/S) = S. We’re asked for the value of R in terms of S.
Typically, when the phrase “in terms of” appears in a question, an Algebraic approach is required. However, this question can be solved rather easily by TESTing VALUES.
IF… S = 2, then root(R/S) = 2… meaning that R/2 has to equal 4. This means that R = 8… so we’re looking for an answer that equals 8 when S = 2. The answers are simple enough that you should be able to find the correct answer in a matter of seconds…
Final Answer: D
GMAT Assassins aren’t born, they’re made,
Rich
