SOLUTION: I am trying to find an equation for direct and indirect variation. The word problem I am working on is: A formula relating the approximate weight of an average person and his heig

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Question 908510: I am trying to find an equation for direct and indirect variation. The word problem I am working on is: A formula relating the approximate weight of an average person and his height states that weight is directly proportional to the cube of height in inches. If a person five feet tall should weigh 108 pounds, how much should a person five feet ten inches tall weigh approximately.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39620)   (Show Source): You can put this solution on YOUR website!
Assign some variables.
w for weight
h for height
k proportionality constant

weight is directly proportional to the cube of height in inches.
Notice, "DIRECTLY PROPORTIONAL".


Next are given, h=5, w=108.
You need to use this to find the value of k.




The formula is

Finally the question is to find w if h is 5 feet 10 inches. Convert this into a decimal value
OR into an improper fraction, but finish the result as either decimal value or mixed number.
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

I am trying to find an equation for direct and indirect variation. The word problem I am working on is: A formula relating the approximate weight of an average person and his height states that weight is directly proportional to the cube of height in inches. If a person five feet tall should weigh 108 pounds, how much should a person five feet ten inches tall weigh approximately.


Let weight be W

Height of 5', in inches, or h: 5(12), or 60"

Then we get: 

 ------- Substituting 108 for W, and 60 for h



, or 



Height of 5' 10", in inches: 5(12) + 10, or 60 + 10, or 70"





Approximate weight of a 5' 10" individual, or W:  lbs 

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