Measures: length, mass, capacity, time, area and volume
Converting between metric units, working with time, and finding perimeter, area and volume.
📌 Key points
- 1 km = 1000 m, 1 m = 100 cm, 1 cm = 10 mm, so 1 m = 1000 mm.
- 1 kg = 1000 g and 1 litre = 1000 ml.
- To change to a smaller unit, multiply (3.5 kg = 3500 g). To change to a larger unit, divide (750 ml = 0.75 litres).
- 60 seconds = 1 minute, 60 minutes = 1 hour and 24 hours = 1 day. 3:45 pm is 15:45 on the 24-hour clock.
- Perimeter is the distance all the way around a shape: add the lengths of all the sides.
- Area is the space inside a flat shape, measured in squares such as cm2. Area of a rectangle = length × width.
- The area of a right-angled triangle is half of the rectangle around it: 12 × base × height.
- Volume is the space inside a 3D shape, measured in cubes such as cm3. Volume of a cuboid = length × width × height.
- To read a scale, first work out what each small mark is worth.
📖 Key words
- Perimeter
- The total distance around the edge of a shape.
- Area
- The amount of flat surface a shape covers, measured in square units.
- Volume
- The amount of space a 3D object takes up, measured in cubic units.
- Capacity
- How much a container can hold, measured in litres or millilitres.
- Mass
- How heavy something is, measured in grams or kilograms.
- Cuboid
- A 3D shape with 6 rectangular faces.
- Compound shape
- A shape made of two or more simple shapes joined together.
✏️ Worked example
A rectangular garden is 12 m long and 7 m wide. Find its perimeter and its area.
- Perimeter = 12 + 7 + 12 + 7 = 38 m.
- Area = length × width = 12 × 7 = 84.
- Area is measured in square units, so the area is 84 m2.
- Answer: the perimeter is 38 m and the area is 84 m2.
Change all the measurements to the same unit before you calculate, and give area in square units and volume in cubic units.
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