The idea, step by step
Use the labels that are present
A scale does not need a number at every tick. Find two labels, work out their difference and divide by the gaps. On the scale from 20 to 60 mL there are eight gaps, so each gap is worth 5 mL.
Start at a nearby known label and count on. A pointer one small gap after 40 is at 45 mL. The missing printed number does not make the gap a different size.
Estimate between ticks
If a pointer is exactly on a tick, read that tick's value. If it is between ticks, the instrument may only support an estimate. Halfway from 20 to 30 is about 25; nearer 20 could be about 22 or 23, depending on the position.
Use words such as about when the scale does not show a finer exact value. Do not invent many decimal places. Check your reading stays between the two surrounding labelled or calculated values.
A common trap
If a number is not printed at the pointer, I cannot read it.
Instead: Equal gaps continue across unnumbered ticks. Use nearby labels to calculate their values.
See the thinking
Fill the silent part of a scale
Read the pointer on the partially numbered millilitre scale.
- 20 to 60 is a difference of 40 mL across eight gaps.
- 40 ÷ 8 = 5 mL per gap.
- The pointer is one gap after 40, so the reading is 45 mL.
Find a temperature with few labels
The thermometer scale labels only 0, 10 and 20. Read the pointer.
- There are five equal gaps from 0 to 10, so each is 2 °C.
- The pointer is two gaps after 10.
- 10 + 2 + 2 = 14 °C.
Check your understanding
There are four equal gaps between 20 and 40 mL. What is the first tick after 20?
Show answer
25 mL
40 − 20 = 20; 20 ÷ 4 = 5; 20 + 5 = 25.
Your turn
6 questions · 11 marks · Work at your own pace.
Read the questions online
- Read the pointer on the millilitre scale.2 marks
- Read the temperature pointer.2 marks
- A scale labels 30 and 50 with four equal gaps between them. Give the three missing tick labels.2 marks
- A pointer is halfway between 60 mL and 80 mL. Estimate its reading.1 mark
- A pointer is between the 10 cm and 11 cm marks, close to 11. Is 10.8 cm or 11.8 cm a sensible estimate?2 marks
- The labels show 100 and 200 grams separated by five equal gaps. The pointer is two gaps after 100. Find the reading.2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Read the pointer on the millilitre scale.2 marks
Each gap is 5 mL.
The pointer is three gaps after 20: 20 + 15 = 35 mL.
35 mL - Read the temperature pointer.2 marks
Each gap is 2 °C.
The pointer is four gaps after 10: 10 + 8 = 18 °C.
18 °C - A scale labels 30 and 50 with four equal gaps between them. Give the three missing tick labels.2 marks
50 − 30 = 20; 20 ÷ 4 = 5.
Count on by 5.
35, 40, 45 - A pointer is halfway between 60 mL and 80 mL. Estimate its reading.1 mark
The halfway amount between 60 and 80 is 70.
About 70 mL. - A pointer is between the 10 cm and 11 cm marks, close to 11. Is 10.8 cm or 11.8 cm a sensible estimate?2 marks
The reading must be between 10 and 11.
11.8 is outside that interval.
10.8 cm. - The labels show 100 and 200 grams separated by five equal gaps. The pointer is two gaps after 100. Find the reading.2 marks
100 ÷ 5 = 20 g per gap.
100 + 2 × 20 = 140.
140 g
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics 2026
Length/mass/capacity/temperature; scaled instruments; partial/unmarked intervals; suitable units and accuracy.
Official curriculum source ↗