Mathematics
Grade 10
15 min
Solve a system of equations using elimination word problems
Solve a system of equations using elimination word problems
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1
Introduction & Learning Objectives
Learning Objectives
Translate a word problem into a system of two linear equations with two variables.
Identify when the elimination method is an efficient strategy for solving a system of equations.
Modify one or both linear equations by multiplication to create opposite coefficients for one variable.
Apply the elimination method to solve for one variable, and then use substitution to solve for the second.
Interpret the numerical solution in the context of the original word problem.
Verify their solution by checking it against the conditions described in the word problem.
Ever wonder how a concert venue knows exactly how many adult and child tickets were sold if they only know the total attendance and total revenue? 🎟️ Let's use algebra to uncover the secrets!
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Key Concepts & Vocabulary
TermDefinitionExample
System of Linear EquationsA set of two or more linear equations that share the same variables. The solution to the system is the point (or set of points) that satisfies all equations simultaneously.The equations `x + y = 10` and `2x - y = 8` form a system. The solution is the specific pair of `x` and `y` values that makes both equations true.
VariableA symbol, usually a letter, that represents an unknown quantity in a mathematical expression or equation.In a problem about the cost of apples and bananas, we might use `a` to represent the cost of one apple and `b` for the cost of one banana.
CoefficientThe numerical factor that is multiplied by a variable.In the term `7d`, which could represent the value of `d` dimes, the coefficient is 7.
Elimination MethodA method fo...
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Core Formulas
Standard Form of a Linear Equation
Ax + By = C
This form is ideal for the elimination method. When you write word problems as equations, arranging them in this standard form aligns the variables and constants vertically, making it easy to add or subtract the equations.
Addition Property of Equality
If a = b and c = d, then a + c = b + d
This is the core principle behind elimination. It allows us to add the left sides of two equations and the right sides of two equations to create a new, valid equation. We do this strategically to eliminate a variable.
Multiplication Property of Equality
If a = b, then ac = bc (where c ≠ 0)
This property lets us multiply an entire equation by a non-zero constant to create an equivalent equation. We use this to create opposite coeffici...
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Challenging
A student is solving the system: `2x + 5y = 4` and `3x - 2y = 13`. They decide to eliminate 'x' and multiply the first equation by 3 and the second equation by -2. They write the following new system: `6x + 15y = 12` and `-6x + 4y = 13`. What error did the student make?
A.They should have multiplied the second equation by +2 instead of -2.
B.They forgot to multiply the constant term in the second equation.
C.They added the coefficients instead of multiplying them.
D.They made a sign error when multiplying the 'y' term in the first equation.
Easy
A movie theater sold 150 tickets for a total of $1550. Adult tickets cost $12 and child tickets cost $8. If 'a' is the number of adult tickets and 'c' is the number of child tickets, which system of equations represents this situation?
A.a + c = 1550, 12a + 8c = 150
B.a + c = 150, 12a + 8c = 1550
C.a - c = 150, 12a + 8c = 1550
D.12a + c = 150, a + 8c = 1550
Easy
In which of the following systems is the elimination method the most efficient strategy to use immediately, without any multiplication?
A.2x + 3y = 7, 2x + 5y = 10
B.4x - 5y = 8, -4x + 9y = 2
C.x + 2y = 3, 3x + 4y = 5
D.5x - y = 1, 10x - 3y = 4
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