Class 8 Maths – Chapter 13
Direct and Inverse Proportions
STEP 2: Simple Examples

Example 1: Direct Proportion

If 5 notebooks cost ₹50, how much will 10 notebooks cost?

Explanation:
More notebooks → More cost (Direct Proportion)

5 notebooks = ₹50
1 notebook = ₹10
10 notebooks = 10 × 10 = ₹100

Example 2: Direct Proportion

A car travels 60 km in 1 hour. How far will it travel in 3 hours?

Explanation:
More time → More distance (Direct Proportion)

Distance in 1 hour = 60 km
Distance in 3 hours = 60 × 3 = 180 km

Example 3: Inverse Proportion

6 workers can complete a work in 10 days. How many days will 3 workers take?

Explanation:
Fewer workers → More days (Inverse Proportion)

Workers × Days = Constant
6 × 10 = 60
3 × ? = 60
? = 60 ÷ 3 = 20 days

Example 4: Inverse Proportion

A bus takes 4 hours at a speed of 40 km/h. How long will it take at 80 km/h?

Explanation:
More speed → Less time (Inverse Proportion)

Speed × Time = Constant
40 × 4 = 160
80 × ? = 160
? = 160 ÷ 80 = 2 hours

⭐ Exam Tip:
Identify the relation first:
• More–More → Direct Proportion
• More–Less → Inverse Proportion