## Introduction

### Measuring time in ancient time?

Time was once measured using the **lengths of shadows** formed at different times of the day.

**Modern way of measuring time:** The modern convention is to divide it into 24 hours, An hour into 60 minutes, and a minute into 60 seconds.

**Vocabulary:**

**Day****Hour****Minute****Second**

### Let’s understand the units of time with some daily basis time.

Today, the usual measuring instruments for time are **clocks and watches**.

#### Hours

Ask the following questions:

**How much time do you take to read?**

**Answer:- **About an hour or even more.

**How much time do you play?**

**Answer:- **About an hour or even more.

#### Minutes

**How much time do you take to drink a glass of milk?**

**Answer:-** Just a few minutes.

**How much time does it take to comb hair?**

**Answer:- **Just a few minutes.

#### Seconds

*Very short durations are expressed in seconds which is the smallest time unit.*

**How much time does it take to kick a ball?**

**Answer:- **Just a second.

### Units of time and relation between them

### Conversion between the units of time

To convert from one unit of **time **to another unit, we need to multiply or divide.

**Example 1**

1. **Convert 67 minutes into seconds.**

**Solution:** 67 min = 67 × 60

**= 4020 sec**

2. **Convert 4 ½ hours into minutes**

**Solution:** 4 ½ hr = 4 × 60 + ½ × 60

= 240 + 30

**= 270 min **

3. **Convert 250 minutes into hours and minutes.**

**Solution:** 1 hr = 60 min or 60 min = 1 hr

250 min = 250/60

**= 4 hr 10 min**

4. **Convert 81 hours into days and hours.**

**Solution:** 1 day = 24 hr or 1 hr = 1/24 day

= 81 hr

= 81/24 hr

**= 3 days 9 hr**

**Example: –** Shelly took 1 hr 27 minutes to cook the food and 240 seconds to get ready for the office. Find the total time she has taken in minutes?

**Solution:** Shelly took 1 hr 27 minutes + 240 seconds

= 1 × 60 + 27 + 240/60

= 60 + 27 + 4

= 91 min

### Concept Map

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