Mathematics
Grade 11
15 min
Solve a system of equations using any method: word problems
Solve a system of equations using any method: word problems
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1
Introduction & Learning Objectives
Learning Objectives
Translate complex word problems into a system of two or more algebraic equations.
Identify and define the unknown variables in a real-world scenario.
Strategically choose the most efficient method (substitution, elimination, or graphical) to solve a given system.
By the end of a this lesson, students will be able to solve systems of linear equations and basic linear-quadratic systems derived from word problems.
Interpret the mathematical solution in the context of the original problem.
Verify the reasonableness of a solution by substituting it back into the problem's context.
An aerospace engineer is calculating the trajectory of a rocket to intercept a satellite. How can they find the exact point in space and time where they will meet? 🚀
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Key Concepts & Vocabulary
TermDefinitionExample
System of EquationsA set of two or more equations with the same set of unknown variables, which are considered simultaneously.A movie theater sold 150 tickets. Adult tickets cost $12 and child tickets cost $8. The total revenue was $1560. This can be modeled by the system: x + y = 150 and 12x + 8y = 1560.
VariableA symbol (usually a letter like x or y) that represents an unknown quantity in a mathematical expression or equation.In the problem 'Find two numbers whose sum is 34 and whose difference is 10,' the variables would be 'x' for the first number and 'y' for the second number.
Substitution MethodA technique for solving a system of equations by isolating one variable in one equation and substituting its value into the other equation....
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Core Formulas
Substitution Method Process
1. Solve one equation for one variable (e.g., y = mx + b). \n 2. Substitute this expression into the other equation. \n 3. Solve the resulting one-variable equation. \n 4. Back-substitute the result to find the other variable.
Use when one variable is already isolated or can be easily isolated without creating fractions.
Elimination Method Process
1. Align equations in standard form (Ax + By = C). \n 2. Multiply one or both equations so that the coefficients of one variable are opposites (e.g., 3y and -3y). \n 3. Add the equations together to eliminate that variable. \n 4. Solve for the remaining variable and back-substitute.
Most efficient when variables are aligned in standard form and have the same or opposite coefficients.
General Form of...
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Challenging
A rectangular plot of land has a perimeter of 82 meters and an area of 400 square meters. What are the dimensions of the plot?
A.20 m by 20 m
B.16 m by 25 m
C.10 m by 40 m
D.8 m by 50 m
Challenging
A manager is trying to follow two new company rules. Rule 1: The number of senior staff (s) plus the number of junior staff (j) must be exactly 50. Rule 2: To maintain a certain budget ratio, three times the number of senior staff plus three times the number of junior staff must equal 165. Why is it impossible for the manager to satisfy both rules simultaneously?
A.The equations result in a negative number of staff members.
B.The two equations are dependent, leading to infinite solutions.
C.The two equations are contradictory, leading to no solution.
D.The problem requires a quadratic equation, not a linear system.
Challenging
The sum of the three digits of a number is 12. The tens digit is two more than the units digit. The number itself is 198 greater than the number obtained by reversing its digits. What is the original number?
A.354
B.264
C.543
D.462
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