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In a certain formula, p is directly proportional to s and

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joyseychow
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In a certain formula, p is directly proportional to s and [#permalink] New post   16 Jul 2009, 03:00
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In a certain formula, p is directly proportional to s and inversely proportional to r. If p =1 when r = 0.5 and s = 2, what is the value of p in terms of r, and s?

(A) s/r
(B) r/4s
(C) s/4r
(D) r/s
(E) 4r/s
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C
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Re: In a certain formula, p is directly proportional to s and [#permalink] New post   17 Jul 2014, 08:09
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joyseychow wrote:
In a certain formula, p is directly proportional to s and inversely proportional to r. If p =1 when r = 0.5 and s = 2, what is the value of p in terms of r, and s?

(A) s/r
(B) r/4s
(C) s/4r
(D) r/s
(E) 4r/s


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Re: VIC [#permalink] New post   16 Jul 2009, 03:19
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P is directly proportional to s means => p = x times s (as s increases p increases, x is constant)
P is inversely proportional to r means => p = y divided by r (as r increases p decreases, y is constant)
So we can say
p= z times s divided by r (z is a constant different from x and y)
When p=1, s =2 and r=0,5
So 1= z*2/0,5
z= 1/4
So p = 1/4*s/r=s/4r

C
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Re: VIC [#permalink] New post   16 Jul 2009, 15:55
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Quote:
In a certain formula, p is directly proportional to s and inversely proportional to r. If p =1 when r = 0.5 and s = 2, what is the value of p in terms of r, and s?

(A)s/r
(B)r/4s
(C)s/4r
(D)r/s
(E)4r/s


p is directly proportional to s
p is inversely proportional to r

p=s/r
1= x*2 / 0.5
1=x * 4
Therefore x = 1/4

Hence p=s/4r
The OA is C
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In a certain formula, p is directly proportional to s and [#permalink] New post   26 Apr 2015, 11:43
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P is directly proportional to s means => p = x times s (as s increases p increases, x is constant)
P is inversely proportional to r means => p = y divided by r (as r increases p decreases, y is constant)
So we can say
p= z times s divided by r (z is a constant different from x and y)
When p=1, s =2 and r=0,5
So 1= z*2/0,5
z= 1/4
So p = 1/4*s/r=s/4r

In the below stated question the direct proportional and inverse proportional are combined. Because there is written the word "AND" How does this differ from this question? In other word; Why is the "Z" there in this question?

[color=#a0a0a0]If the price of a commodity is directly proportional to m^3 and inversely proportional to q^2, which of the following values of m and q will result in the highest price for the commodity?


Thanks in advance for reply![/color]
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Re: In a certain formula, p is directly proportional to s and [#permalink] New post   18 Nov 2021, 09:16
p=As-----@1
p=B/r---@2
Multiplying both the equations
p^2 = AsB/r = AB r/s= 1 (as p=1)
Therefore, AB=s/r---@3
Now as s=2, r=0.5
AB = 2/0.5 = 4----@4
p^2 = 4r/s
1=4r/s=p which is option E

Bunuel Please see where am I going wrong
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Re: In a certain formula, p is directly proportional to s and [#permalink] New post   01 Feb 2023, 05:55
Hoping that this explanation helps :

P is directly proportional to S.
P is inversely proportional to R.

P -- S
P -- 1/R

So summing it up p -- S/R
Now to equalize it, let us introduce a constant k :
Making P = k * S/R. ------------------- (1)

so the value of the constant k is : k = (P * R)/S

Substitute the values as mentioned in the question :
k = (1 * 0.5)/2 = (1 * 5)/(2*10) = 1/4.

Replace this constant in the first equation --(1).
We get P = S/4R

which is C.

(A) s/r
(B) r/4s
(C) s/4r
(D) r/s
(E) 4r/s
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Re: In a certain formula, p is directly proportional to s and [#permalink] New post   07 Mar 2024, 19:32
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