Class 8 Maths – Chapter 13
Direct and Inverse Proportions
STEP 5: Worksheet – FULL ANSWERS

Section A – Direct Proportion (Solved)

Q1. If 6 notebooks cost ₹180, find the cost of 10 notebooks.

Solution:
Cost ∝ Number of notebooks
Cost of 1 notebook = 180 ÷ 6 = ₹30
Cost of 10 notebooks = 30 × 10 = ₹300

Q2. A car travels 150 km in 3 hours. How far will it travel in 7 hours?

Solution:
Distance ∝ Time
Distance per hour = 150 ÷ 3 = 50 km
Distance in 7 hours = 50 × 7 = 350 km

Q3. 15 kg of rice costs ₹675. Find the cost of 4 kg of rice.

Solution:
Cost per kg = 675 ÷ 15 = ₹45
Cost of 4 kg = 45 × 4 = ₹180

Section B – Inverse Proportion (Solved)

Q4. 10 workers can finish a work in 18 days. How many days will 15 workers take?

Solution:
Workers × Days = Constant
10 × 18 = 15 × x
180 = 15x
x = 180 ÷ 15 = 12 days

Q5. 6 taps can fill a tank in 10 hours. How long will 12 taps take?

Solution:
Taps × Time = Constant
6 × 10 = 12 × x
60 = 12x
x = 60 ÷ 12 = 5 hours

Q6. 20 men can build a wall in 12 days. How many men are required to build it in 8 days?

Solution:
Men × Days = Constant
20 × 12 = x × 8
240 = 8x
x = 240 ÷ 8 = 30 men

📝 Exam Tip:
• Always mention whether it is Direct or Inverse proportion
• Write formula clearly
• Show full calculation
• Box the final answer