SOLUTION: Hi. I need some help with the following problem. Thanks Use the given information to find the constant of proportionality. S varies jointly as p and q. If p = 3 and q = 7, then

Question 124817: Hi. I need some help with the following problem. Thanks
Use the given information to find the constant of proportionality.
S varies jointly as p and q. If p = 3 and q = 7, then S = -21.
k =
Answer by bucky(2189) (Show Source): You can put this solution on YOUR website!
Saying that S varies jointly as p and q means that S is related to the product of p and q as in:
.
S = k*p*q
.
in which k represents the constant of proportionality.
.
You are given that when p = 3 and q = 7, then S = -21. You can use these values to find the
value of k. Substitute 3 for p and 7 for q and -21 for S to get:
.
-21 = k*3*7
.
Multiply out the right side to get:
.
-21 = k*21
.
Divide both sides by 21 ... the multiplier of k ... to get:
.
-21/21 = k
.
This simplifies to
.
k = -1
.
Now return to the original joint variation equation of:
.
S = k*p*q
.
substitute -1 for k and you have the joint variation equation as being:
.
S = -1*p*q = -pq
.
So that is the answer to this problem ... k = -1 and as additional information you have the
additional knowledge that the equation for S is S = -pq
.
Hope this helps you to understand the problem.

RELATED QUESTIONS
Hi Can you help me solve the following problem? Use the given information to find the... (answered by scott8148)

Hi. I'm having trouble with the following problem. Can you help me? Use the given... (answered by MathLover1)

Hi! I'm not sure what exactly I did wrong in this problem. I came up with the answer... (answered by Alan3354)

Hi. I need some help checking the following problem. Find the equation of the... (answered by Mathtut)

Hi all, I was hoping to get some help with the following problem. Find ∆y/∆x (answered by HyperBrain)

Hi. I need some help with the following problem. find all x that will make f(x)=0... (answered by solver91311)

Hi. I need some help with the following problem. find all x that will make f(x)=0... (answered by edjones)

Hi, I need some help with the distributive property.... (answered by jjordan95)

Can anyone help me with ANY of these problems? Please! 1) Solve the following... (answered by stanbon,jsmallt9)