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Direct Variation

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Source: — Problem Solving |

by rijul007 » Wed Oct 19, 2011 8:18 pm
P varies as the product of Q and R
=> P = kQR [here k is a constant]

R = P/kQ

P' = 3*P
Q' = Q/2

R' = P'/kQ' = (3*P)/k(Q/2) = 6*P/kQ
R' = 6 * R
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by shankar.ashwin » Wed Oct 19, 2011 8:21 pm
P = k (Q*R)

R = P/kQ

I am assuming P is tripled so P(new) = 3P
And Q is halved Q(new)=Q/2

Substituting these new values we have,
R(new)=6P/kQ
(or) R(new)=6R
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by Anurag@Gurome » Wed Oct 19, 2011 8:21 pm
silverflamein wrote:P varies as the product of Q and R. If P is trebled ad Q is halved, what is the change in R.

Can someone solve this for me ?
P is directly proportional to Q * R or P = k * QR, where k is any constant.
R = P/kQ
New R = 3P/(k * Q/2) = 6P/kQ = 6R
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by GMATGuruNY » Wed Oct 19, 2011 9:09 pm
silverflamein wrote:P varies as the product of Q and R. If P is trebled ad Q is halved, what is the change in R.

Can someone solve this for me ?
Let P = 2, Q = 2, and R = 1.
P/(QR) = 2/(2*1) = 1.

P tripled = 3*2 = 6
Q halved = (1/2)*2 = 1.
Plugging new P and new Q into P/(QR) = 1, we get:
6/(1*R) = 1.
New R = 6.

Since old R = 1 and new R = 6, R is multiplied by a factor of 6.
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