We compare things by asking which is longer, shorter, taller or heavier. To compare fairly, line things up at the same starting point. A ruler measures length in centimetres. Start at zero, not at the very edge of the ruler.
Writing measurements in a table helps us compare them later. If one seedling is 8 cm and another is 5 cm, the first is 3 cm taller. Measuring the same thing twice and getting the same answer shows we measured carefully.
Worked example
A green ribbon is 12 cm and a red ribbon is 9 cm. Which is longer, and by how much?
- 12 is more than 9, so the green ribbon is longer.
- 12 − 9 = 3.
Answer:The green ribbon is 3 cm longer.
Key words
- measure
- find out how long, tall or heavy something is
- centimetre (cm)
- a small unit of length
- ruler
- a tool for measuring length
- compare
- find out what is the same or different
Practise this
New questions every time.