In Far and Near, we explore how to measure and compare distances in our surroundings. We learn to estimate, measure, and work with units like millimetres (mm), centimetres (cm), metres (m), and kilometres (km).
Key Concepts
- Units of Length:
- 10 mm = 1 cm
- 100 cm = 1 m
- 1000 m = 1 km
Estimating Length: Before measuring, we estimate (guess a reasonable value) to check our measurements make sense.
Measuring Accurately: Use a ruler, scale, or measuring tape. Always place the zero at the starting point.
- Conversion: Change between units to compare or calculate.
- To convert km to m: multiply by 1000
- To convert m to cm: multiply by 100
- To convert cm to mm: multiply by 10
Perimeter: The total distance around a shape. Add all the side lengths.
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Convert 3.5 km to metres.
- 3.5 km = 3.5 x 1000 = 3500 m
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A room is 4 m 50 cm long. Express this in centimetres.
Key formulas
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Find the perimeter of a rectangle with length 8 cm and width 5 cm.
- Perimeter = 2 x (length + width) = 2 x (8 + 5) = 2 x 13 = 26 cm
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A pencil is 14 cm 6 mm long. Express this in mm.
Key formulas
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The distance from school to the park is 1200 m. What is this in km?
- 1200 m / 1000 = 1.2 km
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Key Formulas
Key formulas
Common mistakes
- Confusing when to multiply and when to divide when converting. Remember: going to smaller units (e.g., km to m), multiply. Going to larger units (e.g., m to km), divide.
Summary
Length is measured in mm, cm, m, and km. Multiply to convert to smaller units and divide for larger units. Perimeter = sum of all sides.