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the value of T is

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the value of T is

by sanju09 » Sat Oct 22, 2011 3:47 am
T varies directly as the square of r and inversely as the cube of s. If r is tripled and s is doubled, the value of T is
(A) multiplied by 3/2
(B) multiplied by 6
(C) multiplied by 9/8
(D) multiplied by 2
(E) divided by 2
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by Anurag@Gurome » Sat Oct 22, 2011 4:03 am
sanju09 wrote:T varies directly as the square of r and inversely as the cube of s. If r is tripled and s is doubled, the value of T is
T is directly proportional to square of r.
Hence, if r becomes 3r, T will become (3²)T = 9T

T is inversely proportional to cube of s.
Hence, if s becomes 2s, T will become T/(2³) = T/8

Hence, overall T will become (9/8)T
[spoiler]
The correct answer is C.[/spoiler]
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by GmatKiss » Sat Oct 22, 2011 7:31 am
Not getting it :(
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by rijul007 » Sat Oct 22, 2011 10:19 am
T varies directly as the square of r and inverely as a cube of s

T = k(r^2)/(s^3)

value of T when r is tripled and s is double = T'

T' = k((3r)^2)/((2s)^3) = k(9r^2)/(8s^3) = k * 9/8 * (r^2)/(s^3) = 9/8 * T

Hence C is the correct option.
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by zooki » Sat Oct 22, 2011 11:00 am
T is directly proportional to square if r
i. e. T ∞ r^2
T is Inversly proportional to cube of s
i. e. T ∞ 1/s^3

if r triples we get T ∞ (3r)^2= 3^2*r^2= 9r^2
if s doubles we get T ∞ 1/(2s)^3= 1/(2^3*s^3)= 1/(8s^3)

Therefore, if the given conditions happen, the value of T becomes (9/8)T
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