Mathematics Grade 11 15 min

Solve variation equations

Solve variation equations

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Introduction & Learning Objectives

Learning Objectives Identify direct, inverse, joint, and combined variation from a problem statement. Determine the constant of variation (k) using a given set of conditions. Write the specific variation equation that models a given relationship. Solve for an unknown variable in a variation problem by applying the derived equation. Distinguish between the general form and the specific equation of variation. Apply variation concepts to solve multi-step, real-world problems. Ever wonder why your phone charges faster when the screen is off? 🔋 The relationship between power usage and charging time is a perfect example of variation! This tutorial will teach you how to translate word problems describing relationships between quantities into mathematical equations. You will learn...
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Key Concepts & Vocabulary

TermDefinitionExample VariationA mathematical relationship that describes how one variable changes in a predictable way as another variable (or variables) changes.The total cost of apples (C) varies directly with the number of apples (n) you buy. Constant of Variation (k)A non-zero constant that defines the specific relationship between variables in a variation equation. It acts as a scaling factor.In the equation for the circumference of a circle, C = 2Ï€r, the term '2Ï€' is the constant of variation relating circumference (C) to the radius (r). Direct VariationA relationship where two quantities increase or decrease together. As one variable gets larger, the other gets larger by the same factor.Your total earnings (E) vary directly with the hours you work (h). If you work more h...
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Core Formulas

Direct Variation Formula y = kx Use when a problem states 'y varies directly as x' or 'y is directly proportional to x'. 'k' is the constant of variation. Inverse Variation Formula y = k/x Use when a problem states 'y varies inversely as x' or 'y is inversely proportional to x'. Joint Variation Formula y = kxz Use when 'y varies jointly as x and z'. This can be extended to more than two variables (e.g., y = kxwz). Combined Variation Formula y = (kx)/z A common example of combined variation. Use when 'y varies directly as x and inversely as z'. The variables with direct variation are in the numerator, and those with inverse variation are in the denominator.

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Sample Practice Questions

Challenging
The variable P varies jointly with the square of R and the cube root of T, and inversely with S. If P = 80 when R = 2, T = 64, and S = 5, find P when R = 3, T = 27, and S = 9.
A.75
B.225
C.125
D.67.5
Challenging
In the combined variation equation W = (kXY²)/Z², if X is doubled, Y is tripled, and Z is doubled, what is the resulting effect on W?
A.W is multiplied by 9/4
B.W is multiplied by 9/2
C.W is multiplied by 3/4
D.W is multiplied by 18
Challenging
The specific equation modeling the strength (S) of a rectangular beam is S = 12(wd²)/l, where w is width, d is depth, and l is length. Which of the following initial conditions could have been used to find the constant of variation k=12?
A.S=48, w=2, d=4, l=4
B.S=12, w=1, d=1, l=2
C.S=36, w=3, d=2, l=3
D.S=72, w=2, d=6, l=12

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