An interval is one step from a scale mark to the next. Count the intervals between two numbered marks.
There are 5 intervals between 10°C and 15°C. Each blue bracket shows one interval.
Find the difference.15 − 10 = 5°C
Count the intervals.There are 5 intervals.
Divide to find one interval.5 ÷ 5 = 1°C per interval
Count from a numbered mark.The liquid is 3 intervals above 10°C.10 + (3 × 1) = 13°C
Count the intervals. Start at a numbered mark and count one each time you move to the next mark.
Next, intervals of 2
Use the same method when each interval has a different value.
There are 5 intervals between 20°C and 30°C.
Find the difference.30 − 20 = 10°C
Count the intervals.There are 5 intervals.
Divide to find one interval.10 ÷ 5 = 2°C per interval
Count from a numbered mark.The liquid is 3 intervals above 20°C.20 + (3 × 2) = 26°C
Check the value of an interval on every instrument. Every fifth division has a longer line to help you count.
Your turn
Question 1 of 14 · 0 completed
Start with numbered marks, then whole-number intervals, decimals and the final challenges.
1. Ruler
Start here
The strip starts at zero. Read the mark at its right-hand end.
Find the value of one interval. The reading is on a numbered mark.
Find 0 and 1 cm. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 0 and 1 there is 1 interval. One interval = (1 − (0)) ÷ 1 = 1 cm. The reading is on the numbered mark: 6 cm.
2. Thermometer
Start here
Read the top of the coloured liquid column.
Find the value of one interval. The reading is on a numbered mark.
Find 10 and 15 °C. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 10 and 15 there are 5 equal intervals. One interval = (15 − (10)) ÷ 5 = 1 °C. The reading is on the numbered mark: 15 °C.
3. Ruler
Whole numbers
The strip starts at zero. Read the mark at its right-hand end.
Work out one small interval, then read the scale.
Find 20 and 30 mm. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 20 and 30 there are 10 equal intervals. One interval = (30 − (20)) ÷ 10 = 1 mm. The reading is 7 intervals after 30: 30 + (7 × 1) = 37 mm.
4. Thermometer
Whole numbers
Read the top of the coloured liquid column.
Work out one small interval, then read the scale.
Find 10 and 20 °C. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 10 and 20 there are 5 equal intervals. One interval = (20 − (10)) ÷ 5 = 2 °C. The reading is 4 intervals after 10: 10 + (4 × 2) = 18 °C.
5. Measuring cylinder
Whole numbers
For water, read the bottom of the curved surface (the meniscus) at eye level. The cylinder should stand on a flat surface.
Work out one small interval, then read the scale.
Find 20 and 30 mL. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 20 and 30 there are 5 equal intervals. One interval = (30 − (20)) ÷ 5 = 2 mL. The reading is 1 interval after 30: 30 + (1 × 2) = 32 mL.
6. Gas syringe
Whole numbers
Read the front face of the plunger: the edge nearest the nozzle. The scale increases away from the nozzle.
Work out one small interval, then read the scale.
Find 20 and 30 cm³. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 20 and 30 there are 5 equal intervals. One interval = (30 − (20)) ÷ 5 = 2 cm³. The reading is 2 intervals after 30: 30 + (2 × 2) = 34 cm³.
7. Gas syringe
Whole numbers
Read the front face of the plunger: the edge nearest the nozzle. The scale increases away from the nozzle.
Work out one small interval, then read the scale.
Find 60 and 80 cm³. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 60 and 80 there are 10 equal intervals. One interval = (80 − (60)) ÷ 10 = 2 cm³. The reading is 8 intervals after 60: 60 + (8 × 2) = 76 cm³.
8. Measuring cylinder
Decimals
For water, read the bottom of the curved surface (the meniscus) at eye level. The cylinder should stand on a flat surface.
Work out one small interval, then read the scale.
Find 6 and 8 mL. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 6 and 8 there are 4 equal intervals. One interval = (8 − (6)) ÷ 4 = 0.5 mL. The reading is 1 interval after 6: 6 + (1 × 0.5) = 6.5 mL.
9. Ruler
Decimals
The strip starts at zero. Read the mark at its right-hand end.
Work out one small interval, then read the scale.
Find 2 and 3 cm. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 2 and 3 there are 10 equal intervals. One interval = (3 − (2)) ÷ 10 = 0.1 cm. The reading is 4 intervals after 2: 2 + (4 × 0.1) = 2.4 cm.
10. Analogue ammeter
Decimals
Read the mark at the tip of the needle. The unit A means amperes (amps).
Work out one small interval, then read the scale.
Find 1 and 2 A. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 1 and 2 there are 10 equal intervals. One interval = (2 − (1)) ÷ 10 = 0.1 A. The reading is 7 intervals after 1: 1 + (7 × 0.1) = 1.7 A.
11. Newtonmeter
Decimals
Read the horizontal indicator line. This scale increases downwards as the spring stretches.
Work out one small interval, then read the scale.
Find 2 and 3 N. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 2 and 3 there are 5 equal intervals. One interval = (3 − (2)) ÷ 5 = 0.2 N. The reading is 3 intervals after 2: 2 + (3 × 0.2) = 2.6 N.
12. Newtonmeter
Decimals
Read the horizontal indicator line. This scale increases downwards as the spring stretches.
Work out one small interval, then read the scale.
Find 6 and 8 N. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 6 and 8 there are 10 equal intervals. One interval = (8 − (6)) ÷ 10 = 0.2 N. The reading is 7 intervals after 6: 6 + (7 × 0.2) = 7.4 N.
13. Thermometer
Challenge
Read the top of the coloured liquid column.
Work out one small interval, then read the scale.
Find −5 and 0 °C. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between −5 and 0 there are 5 equal intervals. One interval = (0 − (−5)) ÷ 5 = 1 °C. The reading is 2 intervals after −5: −5 + (2 × 1) = −3 °C.
14. Analogue ammeter
Challenge
Read the mark at the tip of the needle. The unit A means amperes (amps).
Work out one small interval, then read the scale.
Find 0.2 and 0.4 A. Count the equal intervals between those numbered marks, then divide their difference by that number.
Between 0.2 and 0.4 there are 10 equal intervals. One interval = (0.4 − (0.2)) ÷ 10 = 0.02 A. The reading is 8 intervals after 0.2: 0.2 + (8 × 0.02) = 0.36 A.
All 14 questions completed
You have practised whole-number and decimal intervals across six types of equipment, including a reading below zero.