Measuring length with a ruler
Measure a pencil, an eraser and a leaf to the nearest millimetre, then learn to measure correctly with a ruler whose end is worn.
Core concept
In short: Measure things with a ruler the right way, starting from zero.
Read a ruler from the zero mark to the nearest millimetre, and subtract the starting mark if you cannot start at zero
Topic: Measurement
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
- Look at where the object ends in the magnifier. Move the reading slider to that mark.
- Record your measurement when the red marker lines up with the end. Measure the pencil, the eraser and the leaf.
- 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.