Learning Objectives
- Measure weight using standard units (kilogram and gram)
- Convert between kilograms and grams
- Estimate and compare the weight of objects
- Solve word problems involving weight
Key Concepts
Standard Units of Weight
We measure weight in kilograms (kg) and grams (g). Heavier things like a bag of rice or your school bag are measured in kilograms. Lighter things like a biscuit or a pencil are measured in grams. 1 kilogram = 1000 grams. Half a kilogram = 500 grams.
Converting Between Units
To convert kg to g, multiply by 1000. So 2 kg = 2000 g. To convert g to kg, divide by 1000. So 3500 g = 3 kg 500 g. When adding or subtracting weights, first convert everything to the same unit. For example: 2 kg 300 g + 1 kg 800 g = 2300 g + 1800 g = 4100 g = 4 kg 100 g.
Weighing Objects
We use weighing scales to find the weight of objects. Digital scales show the weight on a screen. A pan balance compares the weight of an object with known weights. At a vegetable shop, the shopkeeper uses a scale to weigh vegetables and fruits. Always read the scale carefully to get the correct weight.
Word Problems on Weight
Meena bought 2 kg 500 g of potatoes and 1 kg 250 g of tomatoes. The total weight is 2 kg 500 g + 1 kg 250 g = 3 kg 750 g. If her bag can hold 5 kg, how much more weight can she add? 5 kg - 3 kg 750 g = 1 kg 250 g. Word problems help you apply weight concepts to real life.
Important Terms
- Kilogram (kg): A unit of weight for measuring heavier objects
- Gram (g): A unit of weight for measuring lighter objects
- Weighing Scale: A device used to measure the weight of objects
- Pan Balance: A balance with two pans used to compare weights
- Net Weight: The weight of the contents without the container
Quick Revision
- 1 kg = 1000 g
- 500 g = half kg, 250 g = quarter kg
- kg to g: multiply by 1000; g to kg: divide by 1000
- Convert to the same unit before adding or subtracting
- Use a weighing scale to measure weight accurately
- Common weights: apple ~ 200 g, 1 L water ~ 1 kg