Weigh it, Pour it — Class 4 Mathematics (CBSE)

From the current NCERT Maths Mela Grade 4 book, Chapter 8. We weigh things to see how heavy they are, and we pour to see how much a container holds.

1. Why this chapter matters

We measure weight when we buy vegetables, and capacity when we pour milk or water. Knowing the units (g, kg, mL, L), choosing the right one, and converting between them helps in cooking, shopping, and daily life.

2. Core ideas

Idea 1 — Weight and capacity have units

Weight: grams (g) and kilograms (kg). Capacity: millilitres (mL) and litres (L).

Method 2 — How the units relate

1000 g = 1 kg and 1000 mL = 1 L.

Skill 3 — Choose the right unit; weigh and pour

Use g for light things (a pencil) and kg for heavy (a school bag). Use mL for small amounts (a spoon of medicine) and L for large (a bucket). A balance compares weight; pouring compares capacity.

3. Worked examples

Example 1: How many grams make one kilogram?

1000 g make 1 kg.

Example 2: How many millilitres are in 2 litres?

2 L = 2 × 1000 = 2000 mL.

Example 3: Which is heavier — 1 kg of cotton or 1 kg of iron?

They weigh the same — both are 1 kg (the iron just looks smaller).

4. Activity corner

Use a simple balance and a measuring cup. Compare two objects by weight, and two containers by how much they hold. Write:

• Which object was heavier or lighter
• Which container held more or less
• The maths idea (units of weight and capacity)

5. Common mistakes

• Mistake: Using the wrong unit (weighing a bag in grams only). Fix: Use kg for heavy things and g for light things.
• Mistake: Wrong conversions (1 kg = 100 g). Fix: 1 kg = 1000 g and 1 L = 1000 mL.
• Mistake: Thinking a bigger object is always heavier. Fix: Weight depends on the material, not just size — weigh to be sure.

6. How to write better answers

1. Say whether the question is about weight or capacity.
2. Choose the correct unit (g/kg or mL/L).
3. Convert using 1000 if asked.
4. Write the answer with its unit.

7. Practice set

1. In which units do we measure weight?
2. In which units do we measure capacity?
3. How many grams make 1 kilogram?
4. How many millilitres are in 1 litre?
5. Convert 3 kg into grams.
6. Convert 2500 mL into litres and millilitres.

8. Answer key

1. Grams (g) and kilograms (kg).
2. Millilitres (mL) and litres (L).
3. 1000 g.
4. 1000 mL.
5. 3 kg = 3000 g.
6. 2500 mL = 2 L 500 mL.

9. Quick revision

• Weight: grams (g) and kilograms (kg). Capacity: millilitres (mL) and litres (L).
• 1000 g = 1 kg; 1000 mL = 1 L.
• Use g/mL for small, kg/L for large.
• A balance compares weight; pouring compares capacity.
• Weight depends on material, not just size.