We measure weight (how heavy something is) and capacity (how much a container can hold) every day at home, in markets, and in kitchens. In this chapter we practise conversions, comparisons, and word problems involving these measurements.
Key Concepts
- Units of Weight:
- 1000 grams (g) = 1 kilogram (kg)
- 1000 kg = 1 metric tonne (t)
- Units of Capacity (Volume of liquid):
- 1000 millilitres (ml) = 1 litre (L)
Measuring Weight: Weighing scales or balances are used. Shop scales often show grams and kilograms.
Measuring Capacity: Measuring jugs, cups, or beakers show ml and L.
- Conversion:
- kg to g: multiply by 1000
- g to kg: divide by 1000
- L to ml: multiply by 1000
- ml to L: divide by 1000
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Convert 4.5 kg to grams.
- 4.5 x 1000 = 4500 g
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A bottle holds 750 ml. How many such bottles fill a 3-litre container?
Key formulas
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A bag of rice weighs 2 kg 350 g. Express this in grams.
Key formulas
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A shop has 5 kg of sugar. It sells 1 kg 700 g. How much is left?
- 5 kg = 5000 g; 5000 - 1700 = 3300 g = 3 kg 300 g
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A jug contains 2 L 400 ml of juice. If 650 ml is poured out, how much remains?
- 2 L 400 ml = 2400 ml; 2400 - 650 = 1750 ml = 1 L 750 ml
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Key Formulas
- 1 kg = 1000 g; 1 t = 1000 kg
- 1 L = 1000 ml
- To convert to smaller units: multiply; to larger units: divide
Common mistakes
- Mixing weight and capacity units (grams vs millilitres). They are different — grams measure heaviness, millilitres measure liquid volume.
- Forgetting to carry over when adding or borrowing when subtracting mixed units (e.g., kg and g together).
Summary
Weight uses grams (g) and kilograms (kg). Capacity uses millilitres (ml) and litres (L). Always convert to the same unit before adding or subtracting.