📏 Measuring Length

What your child will learn

• Students will be able to explain why standard units are needed and measure small objects in centimetres with a ruler, starting from the 0 mark.
• Students will be able to estimate lengths in cm or m before measuring and choose the sensible unit for an object.
• Students will be able to state 1 m = 100 cm and convert between whole metres and centimetres (up to 9 m).
• Students will be able to add and subtract lengths in the same unit to solve word problems, including how much more is needed.

Lessons in this unit

1. From hand-spans to centimetres: Measure a table with different children's hand-spans, see the answers differ, then introduce the centimetre and measure small objects with a ruler from the 0 mark.
2. Metres, estimating and choosing units: Introduce the metre with a metre stick or tape, estimate lengths of classroom objects in cm or m before measuring, and choose the sensible unit (cm, m, km) for different things.
3. Metres and centimetres together: Show that 1 m = 100 cm using a metre tape, convert whole metres to cm and cm to m and cm (e.g. 250 cm = 2 m 50 cm), and read a height chart.
4. Adding and subtracting lengths: Solve word problems by adding or subtracting lengths in the same unit (cm with cm, m with m), including total length, how much is left and how much more is needed. Convert first only when both lengths are simple.

Key words

centimetre (cm)

A small unit, about the width of your little finger nail.

metre (m)

A big unit, about one long step. 1 m = 100 cm.

kilometre (km)

A very long distance, like from one village to the next.

estimate

A careful guess before measuring.

ruler / measuring tape

Tools with cm marks to measure length.

Help your child at home

What to watch for

Start measuring from the end of the ruler or from 1, not from 0.

Help: Line up the 0 mark with the end of the object. Starting at 1 makes every length 1 cm too long.

Bigger unit means the object is bigger: 1 m of cloth is 'more' than 200 cm of cloth.

Help: Lay them side by side. 200 cm is 2 m, which is longer than 1 m.

1 m = 10 cm.

Help: Count the cm on a metre tape: 100. 1 m = 100 cm, like 1 hundred = 100 ones.

Add the numbers even when the units differ: 1 m + 65 cm = 66.

Help: Change to the same unit first: 1 m = 100 cm, so 100 cm + 65 cm = 165 cm.

Try this at home

• Measure a pencil correctly
• Estimate the door height then measure
• 3 m to cm
• Ribbon 85 cm, cut 38 cm

Quick questions to ask aloud

1. Riya measures the table as 8 hand-spans and Arjun measures it as 10 hand-spans. Why are the answers different? (Their hands are different sizes / One of them counted wrong / The table changed size)
   Show answer

   Their hands are different sizes. Hand-spans differ from person to person. That is why we use centimetres, which are the same for everyone.
2. Which unit is best for measuring the length of a classroom? (Metres / Centimetres / Kilometres)
   Show answer

   A classroom is a few big steps long. Metres give a sensible number, like 7 m.
3. How many centimetres are in 3 metres?
   Show answer

   1 m = 100 cm. 3 m = 100 + 100 + 100 = 300 cm.

Parent guide: how to help your child with Class 3 Maths

Frequently asked questions

What will my child learn in "Measuring Length" (Class 3 Maths)?

Your child will be able to: explain why standard units are needed and measure small objects in centimetres with a ruler, starting from the 0 mark.; estimate lengths in cm or m before measuring and choose the sensible unit for an object.; state 1 m = 100 cm and convert between whole metres and centimetres (up to 9 m).; add and subtract lengths in the same unit to solve word problems, including how much more is needed..

How does MangoMindz teach "Measuring Length"?

In 4 short parts (From hand-spans to centimetres, Metres, estimating and choosing units, Metres and centimetres together, Adding and subtracting lengths). Each part has a picture-based lesson read aloud by Mango Teacher, a quick check, and a quiz built from common mistakes children make, with Mango, a study buddy, for questions.

How long does "Measuring Length" take?

About 110 minutes in total, spread over 4 parts of 15–25 minutes each.

How can I help my child with "Measuring Length" at home?

Work through a small example together, such as: Measure a pencil correctly; Estimate the door height then measure. Then ask a quick question aloud: Riya measures the table as 8 hand-spans and Arjun measures it as 10 hand-spans. Why are the answers different? (Their hands are different sizes / One of them counted wrong / The table changed size)

What mistakes do children often make in "Measuring Length"?

Start measuring from the end of the ruler or from 1, not from 0. Fix: Line up the 0 mark with the end of the object. Starting at 1 makes every length 1 cm too long. Bigger unit means the object is bigger: 1 m of cloth is 'more' than 200 cm of cloth. Fix: Lay them side by side. 200 cm is 2 m, which is longer than 1 m. 1 m = 10 cm. Fix: Count the cm on a metre tape: 100. 1 m = 100 cm, like 1 hundred = 100 ones.

Is "Measuring Length" free on MangoMindz?

Yes. Every lesson part and quiz in "Measuring Length" is free on MangoMindz, with no ads.