AlgèbreFacile
Math Learning PlatformProportionality and Functions
Advanced
📚 arithmetique
📖 About this lesson
Study proportional situations and their representations
Lesson Content
Advanced Proportionality
Direct proportionality
y = kx where k is the proportionality coefficient.
Properties
- •Graph: line through origin
- •If x doubles, y doubles
- •Proportionality table
Inverse proportionality
y = kx or xy = k (constant)
Properties
- •If x doubles, y is divided by 2
- •Graph: hyperbola
- •Applications: speedtime, flowduration
Percent change
Increase
New value = Initial value × (1 + t100)
Decrease
New value = Initial value × (1 - t100)
Successive changes
Increase of t₁% then t₂%: Global coefficient = (1 + t₁/100) × (1 + t₂/100)
Scales
Scale = Distance on map / Real distance
Scale 1:50,000 means 1 cm → 50,000 cm = 500 m
Applications
- •Cooking recipes
- •Maps and plans
- •Exchange rates
- •Mixtures and concentrations
Practical Examples
1
Example 1
📋 Problem
Un article coûte 80€. Il augmente de 25% puis diminue de 20%. Quel est le prix final ?
✅ Solution
80€
💡 Explanation
80 × 1,25 × 0,8 = 80€. Le prix revient à sa valeur initiale