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Grade 6 Beginner About 15 min Version 1 Awaiting review Premium

Measuring length with a ruler

Length is measured in metres (m), centimetres (cm) and millimetres (mm): 1 m = 100 cm and 1 cm = 10 mm. On a ruler, the long numbered marks are centimetres and the small marks between them are millimetres. To measure an object, line up one end with the 0 mark, look straight down at the other end and read the mark it reaches. If the end of the ruler is worn, start at another mark, such as 1 cm, and subtract it from your reading.

What you will learn

  • Measure length to the nearest millimetre with a ruler.
  • Convert between millimetres, centimetres and metres.
  • Correct for a ruler whose zero mark cannot be used.

Before you start

  • Count in tenths (0.1, 0.2, …).

Materials

  • A pencil, an eraser, a leaf, a key and a notebook

Equipment

  • 30 cm ruler marked in millimetres
  • Measuring tape for longer objects

Procedure

  1. Look at where the object ends in the magnifier. Move the reading slider to that mark.
  2. Record your measurement when the red marker lines up with the end. Measure the pencil, the eraser and the leaf.
  3. Use the worn ruler, which starts at 1 cm. Read the end of the leaf and subtract 1 cm.

How this simulation is simplified

  • Each object lies straight along the ruler and you look straight down at the marks.