Solve Proportion Problems Instantly

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Proportion Calculator

Find Third Proportional

Find Fourth Proportional

Example Problems

Finding Third Proportional

Given: 8 : 12

Find x where 8 : 12 = 12 : x

Solution:

  1. Set up the proportion: 8/12 = 12/x
  2. Cross multiply: 8x = 12 × 12
  3. Solve for x: x = 144/8 = 18

Finding Fourth Proportional

Given: 3 : 4 = 9 : x

Solution:

  1. Set up the proportion: 3/4 = 9/x
  2. Cross multiply: 3x = 4 × 9
  3. Solve for x: x = 36/3 = 12

Learn About Proportions

Basic Concepts

  • What is a proportion?
  • Types of proportions
  • Real-world applications

Solving Methods

  • Cross multiplication
  • Step-by-step guides
  • Common mistakes

Practice Problems

  • Beginner exercises
  • Advanced problems
  • Word problems

Complete Guide to Proportional Relationships

A proportion is a mathematical statement that two ratios are equal. Understanding proportions is crucial for solving various real-world problems, from scaling recipes to calculating distances on maps. The basic form of a proportion is a:b = c:d or a/b = c/d.

Concept Definition Example
Direct Proportion When two quantities increase or decrease in the same ratio Time and distance at constant speed
Inverse Proportion When one quantity increases as the other decreases in the same ratio Speed and time for fixed distance
Cross Product Product of means equals product of extremes In a:b = c:d, ad = bc

Spotlight: The Golden Ratio

The Golden Ratio (approximately 1.618) is perhaps the most famous proportion in mathematics and art. It appears in nature, architecture, and design, creating what many consider to be perfectly balanced proportions.

In Nature

  • Spiral shells
  • Flower petals
  • Pine cone patterns

In Art

  • Mona Lisa
  • Parthenon
  • Modern logos

Quick Tips

  • 1 Always cross multiply to check your answers
  • 2 Look for patterns in related proportions
  • 3 Simplify fractions when possible

Common Mistakes

× Forgetting to align corresponding terms
× Mixing up direct and inverse proportions
× Not checking units of measurement

Ready to Master Proportions?

Try our interactive calculators and practice problems to improve your skills!

Practice with Real Examples

Easy Basic Proportions
Find the third proportional:
7 : 10.50
Result: 15.75 See solution
Medium Mixed Numbers
Find the third proportional:
15 : 33
Result: 72.60 See solution
Challenging Decimal Proportions
Find the fourth proportional:
12.50 : 18.75 = 3 : x
Result: 4.50 See solution
Advanced Larger Numbers
Find the fourth proportional:
50 : 69 = 27 : x
Result: 37.26 See solution