Maths Angel Logo
Maths Angel

Direct Proportion Formula and Examples

Learn how direct proportion works using y=kxy = kx and how to find the constant k. Let’s get started! 🚀

Direct Proportion Formula and Examples - introduction visual

Video Lesson

Watch and learn the basics

Flashcards

Review key concepts visually

The definition of direct proportion with notation y∝x and formula y=kx (k is a constant).Direct proportion example: y = kx with x=4, y=20 giving k=5, so y=5x and when x=10, y=50.Direct proportion to x² example: x=3, y=18 gives k=2, so y=2x² and when x=6, y=72Direct proportion to √x example: x=49, y=14 gives k=2, so y=2√x and when x=100, y=20.

🛎️ What Is Direct Proportion?

  • Two quantities are in direct proportion if they increase or decrease together.
  • If x doubles, then y also doubles.

🛎️ Direct Proportion Formula

  • We use the formula y = kx, where k ≠ 0.
  • A constant means k stays the same, when x and y change.

🛎️ Example: Direct Proportion to x²

  • If y is directly proportional to x², we write y = kx².
  • Find k first using given pairs, then substitute the x value to find the wanted y value.

🛎️ Example: Direct Proportion to √x

  • If y is directly proportional to √x, we write y = k√x.
  • Find the constant k first, then use the formula to calculate the wanted y value.

Practice Questions

Test your understanding

Interactive Activity

Explore direct proportion with different relationships.

Loading interactive widget...

Course Overview
Next Lesson

Click here to open ChatCat

Maths Angel Logo
Maths Angel

Our Services

All CoursesChatCat AI

Support

PricingContact Us

© 2026 Maths Angel. All rights reserved.

Privacy PolicyTerms of ServiceCookies