If x/y = 3/z, then 9y² =

Question

Tough and Tricky questions: Algebra.

If x/y = 3/z, then 9y^2 =

A. x²/9
B. x²z
C. x²z²
D. 3x²
E. (1/9)x²z²

Kudos for a correct  solution .

littlewarthog · Answer

The answer is E.

We can solve the equation for y:

\frac{x}{y}=\frac{z}{3}=> y=\frac{xz}{3} .

We square that fraction and get:
 y^2=\frac{x^2z^2}{9}=\frac{1}{9}*x^2z^2

VladimirKarpov · Answer

xz=3y
(xz)^2=(3y)^2
(x^2)(z^2)=9y^2

The answer is C

littlewarthog · Answer

Sh.... didn't read the question stem properly... I guess I was too tired already.

PareshGmat · Answer

Answer = C. x²z²

\frac{x}{y} =\frac{3}{z}

y = \frac{xz}{3}

y^2 = \frac{x^2 z^2}{9}

9y^2 = x^2z^2

g106 · Answer

x/y = 3/z

xz = 3y 
x²z² = 3y²

Ans C

sunita123 · Answer

Answer is C
x/y=3/z 
=>y = zx/3
9y^2= 9*z^2x^2/9=z^2x^2

Viver · Answer

x/y=3/z. y=xz/3.
9y²=9*(x*z/3)^2 =(9x^2 *z^2 )/9=x^2*z^2.

Correct answer C.

Bunuel · Answer

OFFICIAL SOLUTION:

(C) This question is most easily solved by isolating y in the equation and substituting into the expression 9y²:
x/y = 3/z
x = 3y/z
3y = xz
y = xz/3.

If we substitute xz/3 into the expression for y, we get: 
9(xz/3)² = 9(x²z²/9) = x²z².

The correct answer is choice (C).

maxbm10 · Answer

The soution

(x/y) = 3/z
3y = x*z
9y^2 = x^2 * z ^2

regards

Nups1324 · Answer

Hi Bunuel , Need a very small confirmation. In 9y^2, the square is only for the variable y. Had it been like (9y)^2 then the square would've been for both 9 as well as y, right? Thank you.

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yashikaaggarwal · Answer

Yes, GMAT Don't leave question ambiguous. Had it been (9y)^2 the squaring would have been done on both, number as well as variable but having no other brackets in the question the square represent Y^2 only. Even if we don't solve like this 9y^2 can be solve by squaring original equation.
X/y = 3/z
Squaring them,
X^2/y^2 = 9/z^2
Cross multiplication
9y^2 = x^2z^2
Answer

Nups1324 · Answer

Oh.! Duly noted. Thank you so much

If x/y = 3/z, then 9y² =

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