CBSE Class 3 Maths: Time Goes On (Chapter 7)

What is Time and Why Do We Measure It?

Time is like an invisible stream that keeps flowing forward, never stopping. It helps us understand when things happen and how long they last. Think about it: without time, how would you know when to wake up, when your favorite cartoon starts, or when it's your birthday? Time gives order to our lives and helps us plan.

We measure time using different units, just like we measure length in metres or weight in kilograms. The smallest unit we often talk about is a second. Then comes a minute, which has 60 seconds. An hour has 60 minutes. A full day has 24 hours, covering one cycle from morning to night and back to morning. Seven days make a week, and there are about four weeks in a month. Lastly, 12 months make up a year, which has 365 days (or 366 in a leap year!). Knowing these units helps us keep track of everything from a short break to a long vacation.

Reading an Analog Clock: Hours and Minutes

1. Step 1: Understand the Hands — An analog clock has two main hands: a short, thick hand called the hour hand, and a long, thin hand called the minute hand. Sometimes there's a very thin, fast-moving hand called the second hand, but we'll focus on hours and minutes for now. The numbers 1 to 12 are marked on the clock face.
2. Step 2: Read the Hour Hand — Look at the hour hand first. It points to the hour. If it's pointing exactly at a number, that's the hour. If it's between two numbers, it means the hour has just passed the smaller number. For example, if it's between 3 and 4, the hour is 3.
3. Step 3: Read the Minute Hand — Now, look at the minute hand. This hand tells us the minutes past the hour. Each number on the clock (1 to 12) also represents a multiple of 5 minutes. Start from 12 (which is 0 minutes or 60 minutes) and count by 5s for each number the minute hand passes: 1 = 5 minutes 2 = 10 minutes 3 = 15 minutes ... and so on, until ... * 11 = 55 minutes
4. Step 4: Combine to Tell the Time — Put the hour and minute together. For example, if the hour hand is between 4 and 5 (meaning it's 4 o'clock) and the minute hand is pointing at 6 (which is 30 minutes), the time is 4:30. This means 'four thirty' or 'half past four'.

Converting Between Time Units

• Example 1: Converting Hours to Minutes Question: How many minutes are there in 3 hours? Solution: We know that 1 hour = 60 minutes. So, to find minutes in 3 hours, we multiply: 3 hours × 60 minutes/hour = 180 minutes. * Answer: There are 180 minutes in 3 hours.
• Example 2: Converting Days to Hours Question: How many hours are there in 2 days? Solution: We know that 1 day = 24 hours. To find hours in 2 days, we multiply: 2 days × 24 hours/day = 48 hours. * Answer: There are 48 hours in 2 days.
• Example 3: Converting Weeks to Days Question: Your summer vacation is 4 weeks long. How many days is that? Solution: We know that 1 week = 7 days. To find days in 4 weeks, we multiply: 4 weeks × 7 days/week = 28 days. * Answer: Your summer vacation is 28 days long.

Important Time Facts to Remember

• 1 minute = 60 seconds
• 1 hour = 60 minutes
• 1 day = 24 hours
• 1 week = 7 days
• 1 month ≈ 4 weeks (some months have 30 days, some 31, February has 28 or 29)
• 1 year = 12 months
• 1 year = 365 days (a leap year has 366 days, occurring every 4 years)

Avoid These Common Mistakes!

When working with time, it's easy to make small errors. Here are a few to watch out for:

1. Confusing Hour and Minute Hands: Remember, the minute hand is usually longer and thinner, and it moves faster. The hour hand is shorter and thicker.
2. Counting Minutes Incorrectly: Don't treat the minute hand like the hour hand. Each number on the clock for minutes means 'times 5'. So, if the minute hand is at 4, it means 4 x 5 = 20 minutes, not 4 minutes!
3. Forgetting Basic Conversions: Always remember that 1 hour is 60 minutes, not 100! Similarly, 1 day is 24 hours, not 10 or 12.
4. AM and PM Confusion: AM is for morning (midnight to noon), and PM is for afternoon/evening (noon to midnight). If a question mentions 'morning' or 'evening', make sure you're thinking of the correct part of the day.

Practice Questions with Solutions

• Q: What time is shown on a clock if the hour hand is pointing between 9 and 10, and the minute hand is pointing exactly at 4? A: Step 1: Identify the hour. The hour hand is between 9 and 10, so the hour is 9. Step 2: Identify the minutes. The minute hand is at 4. We multiply 4 by 5 to find the minutes: 4 × 5 = 20 minutes. Step 3: Combine hour and minutes. The time is 9:20. Final answer: 9:20
• Q: How many minutes are there in 5 hours? A: Step 1: Recall the conversion for hours to minutes. We know that 1 hour = 60 minutes. Step 2: Multiply the number of hours by 60. So, 5 hours × 60 minutes/hour = 300 minutes. Final answer: There are 300 minutes in 5 hours.
• Q: Riya started reading a book at 3:15 PM and finished reading at 4:00 PM. For how long did she read? A: Step 1: Find the time from 3:15 PM to 3:30 PM. This is 15 minutes (30 - 15 = 15). Step 2: Find the time from 3:30 PM to 4:00 PM. This is 30 minutes (60 - 30 = 30). Step 3: Add the minutes from both steps: 15 minutes + 30 minutes = 45 minutes. Alternatively: From 3:15 PM to 4:15 PM is 1 hour. From 3:15 PM to 4:00 PM is 15 minutes less than 1 hour (60 - 15 = 45 minutes). Final answer: Riya read for 45 minutes.
• Q: A school trip will last for 3 days. How many hours will the trip be? A: Step 1: Recall the conversion for days to hours. We know that 1 day = 24 hours. Step 2: Multiply the number of days by 24. So, 3 days × 24 hours/day = 72 hours. Final answer: The school trip will be 72 hours long.

Frequently Asked Questions