Solving Linear Simultaneous Equations by Elimination
A comprehensive lesson on solving linear simultaneous equations using the elimination method, moving from basic addition/subtraction to scaling equations and solving worded problems.
Learning objectives
- Solve linear simultaneous equations by elimination where coefficients of one variable are the same.
- Solve linear simultaneous equations where one or both equations must be multiplied to match coefficients.
- Set up and solve simultaneous equations from worded real-world problems.
Lesson plan (60 minutes)
Introduction · 10 min
Starter: Retrieval of solving linear equations and basic substitution.
Teaching · 15 min
Direct Instruction: Explaining the elimination method for equations with same coefficients.
Guided Practice · 10 min
Guided Practice: Solving two examples together on mini-whiteboards.
Independent Practice · 20 min
Independent Practice: Differentiated worksheets (Support, Core, Stretch).
Review · 5 min
Plenary: Multiple-choice quiz to check for misconceptions.
Key vocabulary
- Simultaneous Equations
- Equations that are true at the same time and share the same variables.
- Coefficient
- The number in front of a variable (e.g., in 4x, 4 is the coefficient).
- Elimination
- The process of removing one variable by adding or subtracting equations.
- Substitution
- Replacing a variable with a specific value or expression.
- Constant
- A value in an equation that does not change (the number without a letter).
Core worksheet (first questions)
- Solve: 3x + 2y = 18 and x + 2y = 10
- Solve: 5x + 3y = 25 and 2x + 3y = 19
- Solve: 4x + y = 11 and 2x - y = 7
- Solve: x + 3y = 11 and 2x + y = 12
Quiz (sample)
1. Solve x + y = 7 and x - y = 3.
- A. x=5, y=2
- B. x=2, y=5
- C. x=7, y=0
- D. x=3, y=4
2. If you have 3x + 2y = 10 and 3x - y = 4, what is the best first step to eliminate x?
- A. Add the equations
- B. Subtract the equations
- C. Multiply the equations
- D. Divide the equations
3. If you add 5x + 7y = 20 and -5x + 5y = 10, what is the resulting equation?
- A. 2y = 30
- B. 12y = 30
- C. 2y = 6
- D. 12y = 6
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