Mathematics Grade 7 15 min

Write and solve equations that represent diagrams

Write and solve equations that represent diagrams

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1

Introduction & Learning Objectives

Learning Objectives Interpret visual information presented in diagrams to identify known and unknown quantities. Translate relationships shown in diagrams into algebraic expressions. Formulate one-variable linear equations that accurately represent given diagrams. Apply inverse operations to solve one-variable equations derived from diagrams. Verify the solution of an equation by substituting it back into the original diagram's context. Use diagrams to model and solve real-world problems involving unknown quantities. Ever looked at a picture or a blueprint and wondered how much of something there was, or how long a piece should be? 📏 Sometimes, diagrams hold all the clues to solve mathematical mysteries! ✨ In this lesson, you'll learn how to turn those visual cl...
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Key Concepts & Vocabulary

TermDefinitionExample EquationA mathematical statement showing that two expressions are equal, always containing an equals sign (=).x + 7 = 15 VariableA symbol, usually a letter, that represents an unknown number or quantity in an equation.In the equation 3y = 21, 'y' is the variable representing the unknown value. DiagramA visual representation of information, often used to show relationships between quantities, parts of a whole, or geometric shapes.A bar model showing a total length divided into two segments, one known and one unknown. One-Variable EquationAn equation that contains only one type of unknown quantity (one variable).2x + 5 = 19 Inverse OperationsOperations that undo each other, used to isolate a variable in an equation (e.g., addition and subtraction, multiplicat...
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Core Formulas

Diagram-to-Equation Translation Rule Identify the known quantities, the unknown quantity (assign a variable), and the mathematical relationship between them (e.g., sum, difference, product, total, perimeter). Represent this relationship using mathematical symbols to form an equation. This rule helps you convert the visual information from a diagram into a symbolic algebraic equation. Look for keywords or visual cues indicating 'total,' 'sum,' 'difference,' 'parts of a whole,' or 'equal parts' to guide your equation setup. Properties of Equality (Inverse Operations) To solve an equation, perform the inverse operation on both sides of the equals sign to isolate the variable. If a number is added to the variable, subtract it from...

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Sample Practice Questions

Challenging
A diagram shows a rectangle with a perimeter of 78 inches. The length is described as '5 more than twice the width (w)'. Which equation represents the perimeter, and what is the width of the rectangle?
A.2w + 5 = 78; w = 36.5
B.2(w) + 2(2w + 5) = 78; w = 11.33
C.w + (2w + 5) = 78; w = 24.33
D.2(w + (2w + 5)) = 78; w = 11
Challenging
A bar model has a total of 100. It's split into three parts: A, B, and C. The diagram includes notes: 'Part B is twice Part A' and 'Part C is 10 more than Part B'. If Part A is represented by 'x', what is the value of x?
A.10
B.18
C.22.5
D.20
Challenging
A diagram shows a rectangle with a perimeter of 40. The length is 'x+4' and the width is 'x'. A student incorrectly writes the equation 'x + (x+4) = 40'. What is the most likely reason for this error?
A.The student calculated the area instead of the perimeter.
B.The student forgot to combine the like terms 'x' and 'x'.
C.The student only added one length and one width, forgetting to double them for the full perimeter.
D.The student used the wrong value for the total perimeter.

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