The learning target
Learners distinguish an object’s length from the number beside its endpoint. Prepare a centimetre ruler, three paper strips and a recording sheet. Cut the strips to 4 cm, 7 cm and 9 cm, checking them yourself before the lesson. Use blunt scissors with appropriate supervision, or prepare all strips beforehand. The cover photograph illustrates the equipment; do not measure an object from that photograph because its scale and cropping are not controlled.
Model an aligned measurement
Place the 7 cm strip with its left edge at the ruler’s zero mark, not necessarily the plastic edge. Keep the strip straight and parallel to the scale. Ask learners to point to the start, the endpoint and the unit. Record: start 0 cm, end 7 cm, length 7 cm. Explain that the numbered marks show positions while the spaces between adjacent centimetre marks represent equal lengths.
Shift the same strip
Move the same strip so it starts at 2 cm and ends at 9 cm. Ask whether moving it made it longer. The length remains 7 cm: 9 minus 2 equals 7. Let learners count the seven centimetre intervals to check the subtraction. A response of 9 cm confuses the endpoint with the distance travelled along the ruler. A response of eight often comes from counting both boundary marks instead of the intervals.
Give three practice rows
Use a sheet with columns headed start, end, length and explanation. Row A: 0 cm to 4 cm. Row B: 3 cm to 10 cm. Row C: 1 cm to 10 cm. Learners may place the prepared strips or inspect a teacher-drawn scale with equal spacing. Ask for the unit in every length answer. Avoid judging a hand-drawn scale by appearance alone if its spacing is not accurate.
Answer key and useful feedback
A is 4 cm, B is 7 cm and C is 9 cm. In every case, subtract the starting position from the ending position. If a learner writes the endpoint, have them move the same strip to zero and compare. If they count marks, shade one interval and ask them to count spaces. If the arithmetic is correct but the unit is missing, request a complete measurement rather than repeating the whole task.
Check transfer and adapt the language
Finish with an unfamiliar example: a ribbon runs from 5 cm to 11 cm; its length is 6 cm. Ask learners to explain why 11 cm is not its length. Offer pointing and oral explanation when writing would hide their reasoning. Translate the column labels and prompts into the teaching language while preserving the numbers, centimetres and subtraction. This task does not depend on Arabic spelling, English grammar or a particular national curriculum.
