# Measuring Length

## Overview

In this chapter, students explore different aspects of measuring length. They engage with real-life and classroom-based activities to understand the use of measuring tools like ropes, measuring tapes, and scales. The chapter introduces both standard and non-standard units of length, estimations, conversions between metres and centimetres, and concepts like **perimeter** through hands-on experiences.

## Key Topics Covered

### 1. Understanding Measurement

* Words like **height**, **length**, **breadth**, **depth**, and **width** are explained as different ways of talking about **length** in various contexts.
* Students identify what type of measurement is used in different situations.

### 2. Measuring with Ropes

* Activities using **1 m, ½ m, and ¼ m** ropes help children understand how to estimate and measure distances like **1 m**, **5 m**, and **10 m**.
* The chapter shows that:

* 1 m = ½ m + ½ m
* 1 m = ¼ m + ¼ m + ¼ m + ¼ m
* ½ m = ¼ m + ¼ m

### 3. Estimation and Actual Measurement

* Activities like **long jump measurement** are used to teach estimation vs actual measurement.
* Students measure distances jumped by classmates and fill out comparison tables.

### 4. Measuring with Centimetres

* Introduction to the **centimetre (cm)** as a smaller unit:

* 1 metre = 100 centimetres.
* Use of a tailor's tape or scale to measure objects like **fingernail**, **eraser**, **ant**, **rajma seed**, etc.

### 5. Fun Measurement Activities

* Measuring how far **toy cars** roll down a ramp.
* Tracking plant growth weekly with a measuring tape.
* Tracing and measuring **hand size** and using it as an estimation unit.

### 6. Metres and Centimetres Conversion

* Conversion practice:

* 1 m = 100 cm
* 1 m 20 cm = 120 cm
* Students match heights and measurements written in both metres and centimetres.

* Problem-solving examples:

* How many 20 cm long stickers are needed to cover a 2 m board?
* Comparing measurements like 1 m 40 cm and 140 cm to check if they're equal.

### 7. Understanding Perimeter

* Perimeter is introduced as the **total length of the boundary** of an object or shape.
* Activities:

* Estimating and measuring the **perimeter** of objects like desks and classroom floors.
* Using **dot grids** to calculate perimeters of various shapes.
* Drawing shapes with a specific perimeter (e.g., 20 cm).
* Comparing perimeters of different shapes and gardens.

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## New Terms and Definitions

| Term | Simple Definition |
| --------------- | ----------------------------------------------------------- |
| Length | How long something is |
| Height | How tall something is |
| Breadth | How wide something is |
| Depth | How deep something goes |
| Metre (m) | A standard unit of length |
| Centimetre (cm) | A smaller unit of length (100 cm = 1 m) |
| Perimeter | The total length around a shape |
| Estimate | A close guess of a measurement |
| Actual Measure | The exact measurement found using a scale or measuring tape |

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## Practice Problems

### Easy (3)

1. **What is the length of a pencil if it covers 15 small divisions on a ruler?**
**Answer:** 15 cm
**Explanation:** Each small division is 1 cm.

2. **Convert 2 metres to centimetres.**
**Answer:** 200 cm
**Explanation:** 1 m = 100 cm, so 2 m = 2 × 100 = 200 cm.

3. **Is 50 cm more or less than 1 metre?**
**Answer:** Less
**Explanation:** 1 m = 100 cm, and 50 < 100.

### Medium (2)

4. **You have a ribbon that is 1 m 30 cm long. Convert it into centimetres.**
**Answer:** 130 cm
**Explanation:** 1 m = 100 cm, so 100 + 30 = 130 cm.

5. **Your book is 25 cm long. Your friend’s book is 40 cm long. Whose book is longer and by how much?**
**Answer:** Friend’s book is longer by 15 cm
**Explanation:** 40 cm – 25 cm = 15 cm.

### Difficult (3)

6. **You made a square with each side 6 cm long. What is the perimeter?**
**Answer:** 24 cm
**Explanation:** Perimeter = 4 × side = 4 × 6 = 24 cm.

7. **A rectangular table is 1 m long and 50 cm wide. Find its perimeter in cm.**
**Answer:** 300 cm
**Explanation:** Convert 1 m to cm = 100 cm. Perimeter = 2 × (100 + 50) = 2 × 150 = 300 cm.

8. **Estimate then measure the width of a door. You estimate 80 cm, and it measures 90 cm. What is the difference?**
**Answer:** 10 cm
**Explanation:** 90 cm – 80 cm = 10 cm.

### Very Difficult (2)

9. **A board is 2 m long. You have decorative strips of 25 cm. How many such strips are needed to fully cover the board?**
**Answer:** 8 strips
**Explanation:** 2 m = 200 cm; 200 ÷ 25 = 8.

10. **You walk around a rectangular park that is 75 m long and 50 m wide. What distance do you walk?**
**Answer:** 250 m
**Explanation:** Perimeter = 2 × (75 + 50) = 2 × 125 = 250 m.

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