If an object begins at the 2 cm mark and ends at the 9 cm mark, its length is 7 cm. The final ruler reading alone does not answer the question. We need the distance between the two readings.
For families exploring schools in Toa Payoh, measuring length offers a useful connection between practical activity and mathematical explanation. CHIJ Primary (Toa Payoh)’s published Mathematics approach provides a local example.
This guide offers an independent family exercise with a ruler and an ordinary object. It is not a school worksheet or a claim about the precise year level at which every child learns the method.
eduKateSG · Neighbourhood education
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1. Understand the context · 2. Try the activity · 3. Review and continue
Contents
Explore, practise and connect · Four chapters
CHAPTER 1 OF 4
1. Connect measurement with the local school
CHIJ Primary (Toa Payoh)’s Mathematics page describes concrete, pictorial and abstract experiences, problem-solving strategies, and mathematical reasoning and communication.
That gives families a practical question: can a learner explain what the ruler marks represent instead of only reading the largest visible number?
The exercise below is separate from the school’s teaching materials. Check current teacher guidance for the terminology, methods and expectations appropriate to the learner.
CHAPTER 2 OF 4
2. Begin at the zero mark
Choose an ordinary pencil or a strip of paper. Place it beside a ruler on a flat surface and align one end with the ruler’s zero mark.
The zero mark may not be exactly at the physical edge of the ruler. Ask the child to locate the printed scale before measuring.
Read the scale at the other end and state the unit. If the end is exactly at the 7 cm mark, the measured length is 7 cm.
If the object ends between whole-centimetre marks, do not silently round or invent precision. Use the smaller divisions if the learner understands them, or clearly label a rough reading as approximate.
CHAPTER 3 OF 4
3. Measure when the starting point is not zero
Now use a simple invented example: one end of a paper strip is at 2 cm and the other is at 9 cm. Find the difference: 9 cm − 2 cm = 7 cm.
Explain why 9 cm is not the strip’s length. It is the reading at one end; the first 2 cm of the ruler lie before the strip begins.
Draw two endpoint marks and label the distance between them. The learner can count the seven one-centimetre intervals before writing the subtraction.
Compare this with a strip placed from 0 cm to 7 cm. Its position along the ruler differs, but its length is the same.
CHAPTER 4 OF 4
4. Check the quantity, alignment and unit
Ask what is being measured: the pencil’s length, a book’s width or the distance between two points. Different quantities need different reference points.
Keep the ruler aligned with the length being measured rather than slanting it across the object. Then check the starting and finishing readings again.
Write the unit with the answer. One metre equals 100 centimetres, so an unexplained number such as 7 does not tell the reader whether it means centimetres, metres or something else.
Finish by asking the child to describe the method to a family member. A useful explanation names the endpoints, the ruler readings and the distance between them—not just the final number.
Sources and scope
School information checked on 13 October 2026 (Singapore time): CHIJ Primary (Toa Payoh): Mathematics. Programmes may change. Family activities are independently written by eduKateSG, not official school tasks. This article does not imply school endorsement, rank schools or guarantee admission or learning results.