The Junk Seller Class 4 NCERT Maths Chapter 6

In the junk seller class 4 ncert chapter, we learn maths through a real-life shop where old newspapers, plastic bottles, iron pieces and other scrap items are bought and sold. This chapter is useful because it connects classroom maths with daily life: reading rates, multiplying money, adding totals, comparing buying and selling prices, and finding how much money is earned. You will also practise kilograms, rupees and simple record-keeping, just like a shopkeeper writes in a notebook. By the end of this guide, you will be able to calculate the cost of scrap items, find total money paid to customers, work out profit in simple cases, and check your answer step by step. YoLearn AI Tutor can also help you draw tables on a sketchpad and solve similar questions slowly, like a patient maths teacher.

What This Chapter Teaches

Maths Chapter 6 the Junk Seller shows that maths is not only for notebooks. A junk seller buys waste materials from people and later sells them to a bigger dealer. For each item, two ideas are important: quantity and rate. Quantity tells how much there is, such as 5 kg newspaper. Rate tells the price for one unit, such as Rs 6 for 1 kg. To find the total price, we multiply quantity by rate. If the junk seller sells the same item for a higher rate, the extra money is the earning or profit. The chapter also trains you to read tables carefully, write units, and avoid mixing kilograms with rupees.

Important Words in the Chapter

Junk seller
A person who buys old or waste items like newspapers, bottles, metal and cardboard, and sells them for recycling.
Rate
The price of one unit of an item. For example, Rs 8 per kg means 1 kg costs Rs 8.
Quantity
The amount of an item, usually measured in kg, pieces or bundles in this chapter.
Total cost
The full amount of money paid. It is found by multiplying quantity by rate.
Profit
The extra money earned when selling price is more than buying price.

How to Solve Junk Seller Money Problems

  1. Read the item and its unit — Check whether the item is measured in kilograms, pieces or bundles. Do not start multiplying until you know the unit.
  2. Find the rate for one unit — Look for words like Rs 5 per kg or Rs 2 for each bottle. This tells the cost of one unit.
  3. Multiply quantity by rate — Use total cost = quantity × rate. For example, 7 kg at Rs 6 per kg means 7 × 6 = Rs 42.
  4. Add totals if there are many items — If a person sells newspaper and bottles together, calculate each amount separately and then add.
  5. Compare buying and selling price for profit — Profit = selling price − buying price. If the seller buys for Rs 40 and sells for Rs 55, the profit is Rs 15.

Worked Examples

  • Example 1: Rani sells 8 kg old newspapers at Rs 6 per kg. Step 1: Quantity = 8 kg and rate = Rs 6 per kg. Step 2: Total money = 8 × 6 = 48. Step 3: Write the unit as rupees. Final answer: Rani gets Rs 48.
  • Example 2: A junk seller buys 5 kg iron at Rs 12 per kg and sells it at Rs 15 per kg. Step 1: Buying cost = 5 × 12 = Rs 60. Step 2: Selling amount = 5 × 15 = Rs 75. Step 3: Profit = 75 − 60 = Rs 15. Final answer: The junk seller earns Rs 15 profit.
  • Example 3: Mohan sells 3 kg newspaper at Rs 7 per kg and 4 plastic bottles at Rs 2 each. Step 1: Newspaper money = 3 × 7 = Rs 21. Step 2: Bottle money = 4 × 2 = Rs 8. Step 3: Total money = 21 + 8 = Rs 29. Final answer: Mohan receives Rs 29.

Exam Tip: Show Units and Small Steps

In CBSE Class 4 maths, many mistakes happen because students write only a number and forget whether it is kg or rupees. Always write the rate, multiply clearly, and add the rupee sign in the final answer. If a question has two items, do not add the quantities first unless the rate is the same. A clean table with Item, Quantity, Rate and Amount makes the answer easy to check.

Common Mistakes to Avoid

  • Do not add quantity and rate. For example, 5 kg at Rs 6 per kg is not 5 + 6; it is 5 × 6.
  • Do not compare profit using only rates if quantities are different. First find the full buying and selling amounts.
  • Do not forget that per kg means for 1 kg. For 9 kg, the rate must be repeated 9 times by multiplication.
  • Do not mix pieces and kilograms. Ten bottles and ten kilograms are different kinds of quantities.

Practice Questions with Solutions

  • Q: Asha sells 6 kg old newspapers at Rs 5 per kg. How much money does she get? A: Step 1: Quantity = 6 kg and rate = Rs 5 per kg. Step 2: Total money = 6 × 5 = 30. Final answer: Asha gets Rs 30.
  • Q: A junk seller buys 9 kg cardboard at Rs 4 per kg. Find the total buying cost. A: Step 1: Quantity = 9 kg and rate = Rs 4 per kg. Step 2: Total buying cost = 9 × 4 = 36. Final answer: The buying cost is Rs 36.
  • Q: Reena sells 7 plastic bottles at Rs 3 each and 2 kg newspaper at Rs 6 per kg. How much does she receive in all? A: Step 1: Money for bottles = 7 × 3 = Rs 21. Step 2: Money for newspaper = 2 × 6 = Rs 12. Step 3: Total money = 21 + 12 = 33. Final answer: Reena receives Rs 33.
  • Q: A junk seller buys 4 kg metal at Rs 10 per kg and sells it at Rs 13 per kg. What is the profit? A: Step 1: Buying cost = 4 × 10 = Rs 40. Step 2: Selling amount = 4 × 13 = Rs 52. Step 3: Profit = 52 − 40 = Rs 12. Final answer: The profit is Rs 12.

Frequently Asked Questions

What is the main idea of The Junk Seller in Class 4 Maths?

The chapter teaches multiplication, addition and money through buying and selling waste materials. It helps students understand rates such as rupees per kg and how totals are calculated.

How do I find the cost when the rate is given per kg?

Multiply the number of kilograms by the rate for 1 kg. For example, 8 kg at Rs 7 per kg gives 8 × 7 = Rs 56.

What is profit in this chapter?

Profit is the extra money the junk seller earns after selling an item for more than the buying cost. Use profit = selling amount − buying cost.

Why should I write units in answers?

Units show whether the number means rupees, kilograms or pieces. Writing units helps avoid mistakes and makes your solution clear for exams.