Algebra Combined and Joint Variation
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Questions and Answers

What is joint variation?

It occurs when one quantity varies directly as the product of two or more other quantities.

The statement y varies jointly as x and z if there exists a nonzero number k such that y = ______, where x≠0 and z≠0, represents joint variation.

kxz

If a rectangle has a length of 2 meters and a width of 5 meters, what is the area of the rectangle?

10 square meters

What is the value of the constant of variation, k, if the area of a rectangle is 60 square feet, its length is 15 feet, and its width is 4 feet?

<p>1</p> Signup and view all the answers

If y varies directly as x and inversely as z, and y = 22 when x = 4 and z = 6, what is the value of the constant of variation, k?

<p>33</p> Signup and view all the answers

What is y equal to when x = 10 and z = 25, given the information from the previous question?

<p>26.4</p> Signup and view all the answers

What is the name for a situation where one quantity varies directly as the product of two or more other quantities?

<p>Joint Variation</p> Signup and view all the answers

What is the formula for joint variation, where y varies jointly as x and z

<p>y = kxz</p> Signup and view all the answers

What does the k represent in the equation for joint variation?

<p>The constant of variation</p> Signup and view all the answers

In joint variation, what constraint is placed on the values of x and z?

<p>x != 0 and z != 0</p> Signup and view all the answers

The area of a rectangle varies jointly as its length and width.

<p>True (A)</p> Signup and view all the answers

If the area of a rectangle is represented by A, its length by l, and its width by w, what is the equation for joint variation?

<p>A = klw</p> Signup and view all the answers

When describing joint variation, is the term "varies inversely" ever used?

<p>No</p> Signup and view all the answers

What does combined variation describe?

<p>A situation where a variable depends on two or more other variables, varying directly with some and inversely with others.</p> Signup and view all the answers

In combined variation, if y varies directly as x and inversely as z, what is the general equation that represents this?

<p>y = kx/z</p> Signup and view all the answers

How do you determine the value of the constant of variation (k) in combined variation?

<p>You use the given values of the variables to solve for <em>k</em>.</p> Signup and view all the answers

Combined variation is a situation where a variable depends on ______ other variables.

<p>two or more</p> Signup and view all the answers

Flashcards

Joint Variation

One quantity varies directly as the product of two or more other quantities.

Joint Variation Equation

y varies jointly as x and z if y = kxz, where k is a constant.

Joint Variation Example

Area of a rectangle varies jointly as its length and width.

Combined Variation

A variable depends on two or more other variables, varying directly with some and inversely with others.

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Combined Variation Equation

y varies directly as x and inversely as z if y = kx/z.

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Constant of Variation

The constant 'k' in a combined variation equation.

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Direct Variation

A relationship where two variables change in the same direction (as one increases, the other increases).

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Inverse Variation

A relationship where two variables change in opposite directions (as one increases, the other decreases).

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Joint Variation Example: Area

Area of a rectangle = length × width. The area varies jointly with length and width.

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Combined Variation Finding 'k'

Given values of x, y, and z, calculate the constant 'k' in a combined variation equation.

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Solving for 'y' (Combined Variation)

Use the equation, with given values of x, z and k, to solve for y.

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Combined Variation Example

y varies directly with x and inversely with z. Solve for a new value of y.

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Constant of Variation (k)

The constant factor that relates two variables in a direct variation. It represents the ratio between the two variables.

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Equation of Direct Variation

The equation that represents a direct variation relationship: y = kx, where 'k' is the constant of variation.

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Identifying Direct Variation

When one variable increases or decreases, the other variable changes in the same direction by a constant multiple.

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Finding the Constant 'k'

To find the constant of variation 'k', divide the value of 'y' by the corresponding value of 'x' in a direct variation.

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Writing the Equation

Once you know the constant of variation 'k', substitute it into the equation y = kx to represent the direct variation.

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Direct Variation Examples

Examples where one quantity depends directly on another, such as: distance traveled vs. time at constant speed, cost of items vs. quantity purchased.

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Direct Variation with Decreasing Values

Direct variation can also occur when both variables decrease, but the constant of variation remains positive.

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Using Direct Variation to Find Unknowns

Given known values of y and x in a direct variation, you can find an unknown value of either y or x by using the equation y=kx.

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Step 1: Find the Constant 'k'

The first step in using direct variation to find unknowns is to calculate the constant 'k' using the given values of y and x.

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Step 2: Use the Equation

After finding the constant 'k', substitute it into the equation y = kx and then plug in the known value to solve for the unknown variable.

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Direct Variation in Word Problems

Direct variation can be applied to solve word problems where one quantity is directly proportional to another.

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Setting Up the Equation (Word Problem)

In a word problem involving direct variation, identify the variables, determine the constant of variation, and write the equation y = kx.

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Direct Variation with Real-World Applications

Direct variation has many real-world applications, such as calculating costs, distances, speeds, and other relationships with proportional change.

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Study Notes

Joint Variation

  • Joint variation occurs when one quantity varies directly as the product of two or more other quantities
  • If y varies jointly as x and z, then y = kxz, where k is a nonzero constant and x ≠ 0, z ≠ 0
  • Example: The area of a rectangle varies jointly as its length and width. If A = 60 sq ft, I = 15 ft, and w = 4 ft, the equation for joint variation is A = klw. Solving for k gives k = 1.

Combined Variation

  • Combined variation describes a situation where a variable depends on two or more other variables
  • It involves direct and inverse variation
  • If y varies directly as x and inversely as z, then y = kx/z, where k is a nonzero constant
  • Example: if y varies directly as x and inversely as z, and y = 22 when x = 4 and z = 6, find y when x = 10 and z = 25.
  • First, find the constant of variation (k). Using the given values, 22 = k(4/6). Solving for k gives k= 33
  • Then, use the constant of variation to find y when x = 10 and z = 25. Y = 33(10/25) = 13.2

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Related Documents

Direct Variation PDF

Description

This quiz delves into the concepts of joint and combined variation in algebra. You'll explore how one quantity can vary directly as a product of others and how to handle scenarios involving both direct and inverse variations. Test your understanding with examples and practical problems.

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