Problem 39 - Algebra 2

Question

Each pair of values is from a direct variation. Find the missing value. $$ (4,6),(x, 3) $$

Step-by-Step Solution

Answer

The missing value x in the direct variation pairs (4,6),(x, 3) is 2.

Step 1: Identify and Apply the Direct Variation Relationship

Since one pair of variations (4,6) is known, the relationship between x and y can be expressed as \(y = kx\), where k is the constant of variation which we calculate from the known pair of values, using the equation \(k = y/x = 6/4 = 1.5\).

Step 2: Substitute the known values into the Direct Variation Relationship

We substitute k = 1.5 and y = 3 into the direct variation relationship to find the unknown x, getting the equation as \(3 = 1.5x\).

Step 3: Solve for the Unknown

By simplifying the above equation, we get \(x = 3/1.5 = 2\). Hence, the unknown value for x is 2.

Key Concepts

Constant of Variation

In mathematics, especially when dealing with direct variation problems, the "constant of variation" is a crucial concept. It represents the rate at which one variable changes relative to another in a proportional relationship.

The constant of variation is typically denoted by the letter \(k\). Its role is to maintain the equation that connects two variables in a linear and directly proportional manner. For example, in the equation \(y = kx\), \(k\) is the constant of variation. In our problem set, using the pair \((4, 6)\), we find \(k\) by dividing \(y\) by \(x\), which gives us \(k = \frac{6}{4} = 1.5\).

Once calculated, \(k\) remains constant for any pair of \(x\) and \(y\) values that are part of this direct variation equation. This means that regardless of the values of \(y\) or \(x\), once you have \(k\), you can always predict the other variable if one of them is known.

Proportional Relationships

Proportional relationships are foundational in algebra and are characterized by two variables maintaining a constant ratio, reflected in their relationship through a consistent constant of variation.

This means that if one variable increases or decreases, the other does as well at a rate defined by \(k\). For direct variation, if you plotted these on a graph, you would see a straight line passing through the origin, showcasing that the ratio between these two variables does not change.

Let's consider our problem: with the pairs \((4, 6)\) and \((x, 3)\), these two pairs are in a direct variation relationship, meaning \(\frac{y_1}{x_1} = \frac{y_2}{x_2}\). By ensuring this ratio equals \(k\), you respect the rules of proportionality. The term “proportional” here means that changes happen at consistent rates relative to each other. This helps predict one variable if you have the value of the constant and the second variable.

Algebraic Equations

Algebraic equations serve as tools to represent relationships between numbers and variables, allowing us to solve for unknowns. In direct variation problems, such as the one given, an algebraic equation like \(y = kx\) effectively models the relationship between the variables.

To find a missing value, we set up an equation using the known constant of variation and one of the remaining variables. For our exercise, we substituted into \(3 = 1.5x\) to find \(x\). By rearranging and solving using simple algebraic manipulations, we determined that \(x = 2\).

The power of algebraic equations lies in their ability to make complex relationships simple and solve them systematically. Through steps like substituting known values and balancing the equation, we can solve for unknowns effectively. These methods not only apply in academics but also in real-life scenarios where relationships between changing quantities need to be determined.