We measure weight to find out how heavy something is. We measure capacity to find out how much liquid a container can hold.
Units of Weight
- The standard unit of weight is the kilogram (kg).
- For lighter things we use grams (g).
- 1 kg = 1000 g
Units of Capacity (Volume of Liquid)
- The standard unit of capacity is the litre (L).
- For smaller amounts we use millilitres (mL).
- 1 L = 1000 mL
Reading a Balance Scale
A balance scale is level when both sides have the same weight. If the left side goes down, the left side is heavier.
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A bag of rice weighs 3 kg 500 g. Write this in grams only.
3 kg 500 g = (3 x 1000) + 500 = 3000 + 500 = 3500 g
A jug holds 2 L 250 mL of water. Write this in mL only.
2 L 250 mL = (2 x 1000) + 250 = 2000 + 250 = 2250 mL
Riya has 5 kg of flour. She uses 2 kg 300 g. How much is left?
5 kg = 5000 g. Used = 2300 g. Left = 5000 - 2300 = 2700 g = 2 kg 700 g
A bottle contains 750 mL of juice. Mohan drinks 3 such bottles. How much juice does he drink?
Total = 750 x 3 = 2250 mL = 2 L 250 mL
A shopkeeper has 10 kg of sugar. He packs it into bags of 500 g each. How many bags does he fill?
10 kg = 10000 g. Number of bags = 10000 / 500 = 20 bags
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Common mistakes
- Mixing up kg and g — always convert to the same unit before adding or subtracting.
- Forgetting that 1 L = 1000 mL (not 100 mL).
Summary
Weight is measured in kg and g (1 kg = 1000 g). Capacity is measured in L and mL (1 L = 1000 mL). Convert to smaller units before calculating.