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Find the value of w help needed

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by rsarashi » Sun Apr 30, 2017 4:09 am
u^2 = k*w^3 ( directly proportional)

8^2 = k*8^3

solving this k=1/8

So, 27^2 = 1/8*w^3

3^3*3^3*2^3=w^3

So w= 18

Please confirm OA?
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by GMATGuruNY » Sun Apr 30, 2017 5:06 am
Hmna wrote:Given that u^2 is directly proportional to the cube of w. Find the value of w when u = 27, if u = 8 when w = 8.

A) 14
B) 16
C) 18
D) 20
u and w are proportioned as follows:
(u�)²/(w�)³ = (u₂)²/(w₂)³.

Plugging in u�=8, w�=8, and u₂=27, we get:

8²/8³ = 27²/(w₂)³

1/8 = 27²/(w₂)³

(w₂)³ = (27²)(8)

(w₂)³ = 3�2³

w₂ = (3�2³)^(1/3) = (3²)(2) = 18.

The correct answer is C.
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