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CBSE Class 3 Mathematics★ 4–5 marks · CBSE Class 3 Mathematics (Math-Magic) Chapter 8

Who Is Heavier?

Measurement of mass — grams and kilograms. Comparing weights using a balance. Standard weights and estimation. CBSE Class 3 Mathematics (Math-Magic) Chapter 8.

⏱ 8 min readEasy difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1Identify units of weight: gram (g) for light things, kilogram (kg) for heavy things
2Estimate weight using benchmarks: paperclip ≈ 1 g, 1-litre water bottle ≈ 1 kg, bag of rice ≈ 5-10 kg
3Compare weights — which is heavier/lighter, and by how much
4Convert between g and kg: 1 kg = 1000 g
5Read a weighing scale (simple kitchen scale or balance) and understand the concept of standard weights

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Why this chapter matters

Weight is the second fundamental measurement after length. This chapter teaches grams (g) for light objects and kilograms (kg) for heavy objects, using relatable benchmarks: a paperclip ≈ 1 g, a bag of rice ≈ 5-10 kg. Children learn to compare weights, use a balance, estimate, and convert between g and kg. Understanding weight is essential for cooking, shopping, health, and science.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

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Class 3 Mathematics Chapter 4: Long and Short

Builds on measurement concepts (units, estimation, comparison) — now applying to weight instead of length.

Who Is Heavier?

What is Weight?

WEIGHT (or MASS) tells us how HEAVY or LIGHT something is.

A FEATHER is LIGHT
A STONE is HEAVY
A BAG OF RICE is HEAVY
A PAPER is LIGHT

Units of Weight

Gram (g)

A GRAM is a SMALL unit. We use it for LIGHT things.

Thing	Approximate Weight
A paperclip	About 1 g
A small pencil	About 5 g
A 1 rupee coin	About 4 g
A slice of bread	About 25 g
A chocolate bar	About 50-100 g

Fun Fact: A small paperclip weighs about 1 gram!

Kilogram (kg)

A KILOGRAM is a BIG unit. We use it for HEAVY things.

Thing	Approximate Weight
A bag of rice	1 kg, 2 kg, 5 kg
A watermelon	About 2-5 kg
A school bag with books	About 3-5 kg
A brick	About 3 kg
A newborn baby	About 3-4 kg

1 kilogram = 1000 grams

Comparing Weights

Which is Heavier?

Object A	Object B	Heavier One
Pencil (5 g)	Book (200 g)	Book
Apple (100 g)	Watermelon (3 kg)	Watermelon
Cotton (1 kg)	Iron (1 kg)	Both SAME weight
Feather (1 g)	Brick (3 kg)	Brick

Important!

1 kg of COTTON and 1 kg of IRON weigh the SAME — 1 kilogram!

Even though cotton is MUCH BIGGER in size, the WEIGHT is the SAME. This is a very important idea in measurement.

Using a Balance

A BALANCE is a tool that compares weights.

Simple Balance

A simple balance has TWO PANS. Put objects in each pan. The HEAVIER side goes DOWN. The LIGHTER side goes UP.

If both sides are EQUAL, the pans are LEVEL

How to Use a Balance

Put the object you want to weigh on the LEFT pan
Put STANDARD WEIGHTS on the RIGHT pan
Keep adding or removing weights until both pans are LEVEL
The weights on the right tell you how much the object weighs

Making a Simple Balance at Home

You need:

A HANGER
Two SMALL BAGS or CUPS
STRING

Tie a bag to each end of the hanger
Hang the hanger on a hook
Put the object in one bag and standard weights in the other
When they balance, you have found the weight!

Standard Weights

Standard weights are objects of KNOWN weight used for measuring.

Common Standard Weights

1 g, 2 g, 5 g, 10 g, 20 g, 50 g, 100 g, 200 g, 500 g
1 kg, 2 kg, 5 kg

Using Standard Weights to Measure

To weigh 350 g of rice:

Put a 200 g weight → still need 150 g
Add a 100 g weight → still need 50 g
Add a 50 g weight → perfectly balanced!
Total: 200 g + 100 g + 50 g = 350 g

Estimation of Weight

ESTIMATION means making a SMART GUESS about weight WITHOUT measuring.

Practice Estimating

Estimate the weight of your MATHS BOOK: ___ g. Now weigh it. How close were you?
Estimate the weight of your WATER BOTTLE (full): ___ g. Now check.
Estimate the weight of your SCHOOL BAG: ___ kg. Now check.

Tips for Better Estimation

Remember that a SMALL PENCIL is about 5 g
Remember that a PACKET OF BISCUITS is about 100-200 g
A BAG OF SUGAR (1 kg) is a good reference for 1 kg
A WATERMELON is about 3-5 kg
YOUR OWN WEIGHT is about 20-30 kg (for Class 3 students)

Real-Life Weight Problems

Problem 1: Shopping

Riya buys 2 kg of rice, 1 kg of sugar, and 500 g of tea. What is the total weight?

Solution:

2 kg + 1 kg + 500 g = 3 kg 500 g
Total weight: 3 kg 500 g

Problem 2: Comparing

A bag of potatoes weighs 5 kg. A bag of onions weighs 3 kg. How much MORE do the potatoes weigh?

Solution: 5 kg - 3 kg = 2 kg Potatoes are 2 kg heavier.

Problem 3: Adding Weights

A fruit seller has:

10 kg of apples
8 kg of mangoes
5 kg of oranges

What is the total weight of fruit?

Solution: 10 + 8 + 5 = 23 kg

Problem 4: Packing

A shopkeeper has 20 kg of sugar. He packs it into 1 kg bags. How many bags can he make?

Solution: 20 ÷ 1 = 20 bags

Common Mistakes

'1 kg of cotton is lighter than 1 kg of iron.' — No! They weigh EXACTLY the same — 1 kg each. The cotton just TAKES MORE SPACE.
'Gram is used for heavy things.' — No! Gram is for LIGHT things. Kilogram is for HEAVY things.
'1000 kg = 1 g.' — No! 1000 g = 1 kg. Kilogram is the BIGGER unit.
'Heavier always means bigger.' — No! A small iron ball is heavier than a large balloon. Size and weight are DIFFERENT.
'A balance tells you the exact weight in grams.' — A balance COMPARES weights. You need standard weights to find the exact weight.

Quick Self-Test

Q1: How many grams are in 1 kilogram? A1: 1000 grams.

Q2: Which is heavier: 1 kg of cotton or 1 kg of iron? A2: Both are the SAME weight (1 kg each).

Q3: What unit would you use to weigh a pencil? A3: Grams (g).

Q4: Convert 3 kg into grams. A4: 3 kg = 3000 g.

Q5: A bag of rice weighs 5 kg. A bag of wheat weighs 8 kg. What is their total weight? A5: 5 + 8 = 13 kg.

Q6: A book weighs 250 g. How many books weigh 1 kg? A6: 1000 ÷ 250 = 4 books.

Q7: What tool is used to compare weights? A7: A balance.

Q8: If you weigh 25 kg and your school bag weighs 3 kg, what is the total weight? A8: 25 + 3 = 28 kg.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Units of weight and their use

Gram (g): very light things — paperclip (~1 g), chocolate bar (~50 g), apple (~150 g), book (~300 g) · Kilogram (kg): heavy things — bag of flour (1 kg), newborn baby (~3 kg), bag of rice (5-10 kg), adult (~60-70 kg)

Choose the right unit: g for small, kg for large. Don't measure a paperclip in kg!

Unit conversion

1 kg = 1000 g · To convert kg to g: multiply by 1000 (3 kg = 3000 g) · To convert g to kg: divide by 1000 (2500 g = 2 kg 500 g) · ½ kg = 500 g, ¼ kg = 250 g

At Class 3 level, focus on 1 kg = 1000 g and simple conversions like 2 kg = 2000 g, ½ kg = 500 g.

Comparing weights

Heavier = more weight. Lighter = less weight. How much heavier = heavier weight − lighter weight. Example: Bag A = 3 kg, Bag B = 2 kg. Bag A is 3−2 = 1 kg heavier than Bag B.

Always use the SAME unit when comparing. Convert 2000 g to 2 kg before comparing with 3 kg.

Weight benchmarks (for estimation)

Paperclip ≈ 1 g · Orange/apple ≈ 150-200 g · 1-litre water bottle ≈ 1 kg · Newborn baby ≈ 2.5-3.5 kg · Bag of rice/atta ≈ 5 kg · Small child (age 8) ≈ 25-30 kg

These benchmarks help children estimate weight without a scale: 'This book feels like 3-4 apples — maybe 500 g?'

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Confusing weight with size — thinking a big object is always heavier

✓ A big balloon is lighter than a small stone. A big empty box is lighter than a small book. Size ≠ weight. Weight depends on what the object is MADE of, not how big it looks.

WATCH OUT

✗ Using the wrong unit — saying 'a pencil weighs 10 kg'

✓ Think: 'Is this light or heavy?' Light → g. Heavy → kg. A pencil is light → about 10 g. Ten kg is like a heavy school bag!

WATCH OUT

✗ Confusing ½ kg with 500 kg (or 500 g with ½ g)

✓ ½ kg = 500 g. Half a kilogram is five hundred grams. It's NOT 500 kg (that would be half a ton!).

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Comparison and estimation

Which is heavier/lighter? Estimate weights of everyday objects; match objects to approximate weights

Questions

Balance and weighing

Reading simple balance/scale; using standard weights; conversion between g and kg

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· Unit

Which unit would you use to weigh a pencil — g or kg?

▶ Show solution

Gram (g). A pencil is very light — about 5-10 grams. Using kg would be like measuring an ant in kilometres.

Q2EASY· Conversion

How many grams are there in 2 kg?

▶ Show solution

2 kg = 2 × 1000 = 2000 grams.

Q3EASY· Compare

Bag A weighs 3 kg. Bag B weighs 2500 g. Which is heavier and by how much?

▶ Show solution

Convert to same unit: 3 kg = 3000 g. Bag A = 3000 g, Bag B = 2500 g. Bag A is heavier by 3000 − 2500 = 500 g (or ½ kg).

Q4EASY· Real-world

A shopkeeper sells rice in 5 kg bags. How many grams of rice are in one bag?

▶ Show solution

5 kg = 5 × 1000 = 5000 grams. One bag contains 5000 g of rice.

Q5MEDIUM· Estimate

Estimate the weight of your school bag with books inside. Is it closer to 1 kg, 3 kg, or 10 kg? Explain your estimate.

▶ Show solution

A school bag with books is about 3 kg. Reasoning: An empty bag is about 500 g. Each textbook is about 300-400 g. With 4-5 books plus notebooks, the total is roughly 2.5-3.5 kg. 1 kg is too light (like a single water bottle), and 10 kg is too heavy (like a big bag of rice).

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Units of weight: gram (g) for light things, kilogram (kg) for heavy things
•1 kilogram (kg) = 1000 grams (g). ½ kg = 500 g, ¼ kg = 250 g
•Weight benchmarks: paperclip ≈ 1 g, apple ≈ 150 g, 1-litre water ≈ 1 kg, bag of rice ≈ 5 kg
•Big size ≠ heavy weight. A large balloon is lighter than a small stone
•To compare weights, use the SAME unit. Convert kg to g (multiply by 1000) or g to kg (divide by 1000)
•Heavier by = larger weight − smaller weight

CBSE marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 4–5 marks in Class 3 Mathematics assessment

Question type	Marks each	Typical count	What it tests
Fill in the blanks / MCQ (1 mark)	1	2	Choosing g or kg; 1 kg = ___ g; identifying heavier/lighter from given weights
Short answer (2 marks)	2	1–2	Comparing weights with conversion; real-world weight estimation; simple word problems

Prep strategy

Kitchen scale activity: weigh 5 everyday objects — an apple, a book, a toy, a spoon, a water bottle
Play 'Heavier or Lighter?': hold two objects, guess which is heavier, then weigh to check
Visit a grocery store — look at packaged weights: 1 kg atta, 500 g butter, 100 g chocolate
Use body as reference: 'You weigh about 25 kg. How many of you equal a 50 kg sack of cement?'
Practice conversions: 'If 1 kg = 1000 g, then half kg = ___ g? Two kg = ___ g?'

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