Linear Equations in Two Variables • Topic 3 of 3

Real-Life Applications

Why Study Linear Equations in Real Life?

Linear equations help model relationships between two quantities that change at a constant rate. They appear everywhere in daily life!

Common Real-Life Situations:

  • Age problems: "Father is twice as old as son"
  • Number problems: "Sum of two numbers is 15"
  • Cost problems: "Fixed cost + variable cost per item"
  • Distance-time: "Distance = speed × time"
  • Mixture problems: "Mixing two solutions"

Steps to Solve Word Problems:

  1. Identify the unknowns and represent them with variables (x, y)
  2. Translate the conditions into linear equations
  3. Solve the equations (find ordered pairs or relationships)
  4. Interpret the answer in the context of the problem

Types of Problems:

Problem TypeExampleEquation Form
NumberOne number is 5 more than anotherx = y + 5
CostTotal cost = price × quantityC = 5x + 3y
GeometryPerimeter of rectangle2(l + w) = 24
Applications of Linear EquationsSpeed-Distanced = s × t → 60t + 0 = dIf t=2 hrs: d=120 kmCost ProblemsCost = Fixed + Variable × n500 + 50n = Total BillAge ProblemsPresent + Future relationshipx + 5 = 2(y + 5)GeometryPerimeter: 2(l+w) = 48Sum of angles: x+y=90Step 1: Define variables Step 2: Form equation Step 3: Solve Step 4: VerifyAlways check the solution satisfies the original context
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Worked Example

Solve a standard problem on Real-Life Applications.

Solution

Apply the formula/method shown in the concept section above.

Key Points

  • Understand the definition and properties of Real-Life Applications.
  • Study the worked examples and practice similar problems.
  • Always verify your answer using the original conditions.
Tap an option to check your answer0 / 4
Q1.Real-life word problems are modelled by:
Explanation: Translate into equations.
Q2."The sum of two numbers is $10$" becomes:
Explanation: $x+y=10$.
Q3.The cost of $x$ pens at $\textsf{Rs }5$ each is:
Explanation: $5x$.
Q4.Two unknown quantities usually require:
Explanation: Two equations.