Chapter 7: Problem 74
Find an equation of variation in which: \(y\) varies jointly as \(x\) and \(z\) and inversely as \(w,\) and \(y=\frac{3}{2}\) when \(x=2, z=3,\) and \(w=4\)
Short Answer
Expert verified
The equation is \( y = \frac{xz}{w} \).
Step by step solution
01
- Understand the problem
Identify that this is a joint and inverse variation problem. The variation statement 'y varies jointly as x and z and inversely as w' translates to an equation of the form: \[ y = k \frac{xz}{w} \] where \( k \) is the constant of proportionality.
02
- Substitute given values to find k
Given values: \( y = \frac{3}{2} \), \( x = 2 \), \( z = 3 \), and \( w = 4 \). Substitute these values into the equation to find \( k \): \[ \frac{3}{2} = k \frac{(2)(3)}{4} \]
03
- Simplify the equation
Simplify the equation to isolate \( k \): \[ \frac{3}{2} = k \frac{6}{4} \] Then, simplify \( \frac{6}{4} \) to \( \frac{3}{2} \): \[ \frac{3}{2} = k \frac{3}{2} \]
04
- Solve for k
Divide both sides by \( \frac{3}{2} \) to isolate \( k \): \[ k = 1 \]
05
- Write the final equation
Substitute \( k \) back into the variation equation: \[ y = k \frac{xz}{w} \] Substituting \( k = 1 \), the final equation is: \[ y = \frac{xz}{w} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
constant of proportionality
In any variation problem, the constant of proportionality plays a key role. It is denoted by the letter \( k \). This constant helps in maintaining the proportional relationship between variables. For example, in the equation \( y = k \frac{xz}{w} \), \( k \) ensures that changes in \( x, z, \) and \( w \) are reflected in \( y \) in a proportional manner.
Think of it as a scaling factor. Once you identify \( k \), you can predict the behavior of the variables under different circumstances.
In this way, the constant of proportionality serves as a bridge, connecting the variables in a meaningful way.
Think of it as a scaling factor. Once you identify \( k \), you can predict the behavior of the variables under different circumstances.
In this way, the constant of proportionality serves as a bridge, connecting the variables in a meaningful way.
proportional relationships
Proportional relationships describe how the variables interact with one another. When two quantities vary jointly, like \( x \) and \( z \) in this exercise, it means they increase or decrease together. On the other hand, if a quantity varies inversely like \( y \) with \( w \), it means \( y \) will do the opposite of \( w \).
In simpler terms:
In simpler terms:
- If \( x \) doubles and everything else stays the same, \( y \) also doubles.
- If \( w \) doubles and everything else stays the same, \( y \) halves.
variation equations
Variation equations are mathematical expressions describing how one variable depends on others. This problem involves a mixed variation, specifically joint and inverse variation. The general formula for joint and inverse variation, in this case, is \( y = k \frac{xz}{w} \).
Let's break it down:
Let's break it down:
- Joint variation: \( y \) depends directly on \( x \) and \( z \). As \( x \) or \( z \) increases, \( y \) increases, given \( w \) stays the same.
- Inverse variation: \( y \) depends inversely on \( w \). As \( w \) increases, \( y \) decreases, given both \( x \) and \( z \) are unchanged.
algebraic manipulation
Algebraic manipulation refers to the processes and techniques used to solve for unknowns in equations. In this exercise:
- First, identify the relationship \( y = k \frac{xz}{w} \)
- Next, substitute the known values into the equation \( \frac{3}{2} = k \frac{(2)(3)}{4} \)
- Simplify the right-hand side \( \frac{3}{2} = k \frac{6}{4} \)
- Further simplify to \( \frac{3}{2} = k \frac{3}{2} \)
- Then isolate \( k \) by dividing both sides by \( \frac{3}{2} \)
- The result is \( k = 1 \)
- Finally, substitute \( k \) back into the main equation to get the final equation \( y = \frac{xz}{w} \)