Racing Seconds 5 Maths Chapter 12 CBSE Notes 2025-26

These revision notes explain the main ideas from Chapter 12 “Racing Seconds” in Class 5 Maths. The chapter introduces the concept of measuring time, how to differentiate between minutes and seconds, and the importance of time in daily activities and competitions. It guides students to understand time using day-to-day examples, conversions, and problem-solving situations, making the concept both engaging and easy to grasp.

Understanding Time Measurement The chapter starts by showing how people do various activities at different times and how long they take. By using examples like Raghav practising yoga, students are encouraged to find out the start and end times of an activity and work out the total time spent. Activities such as “Who took the longest time?” and “Who took the least time?” help students compare durations.

The concept of elapsed time is introduced by examining the difference between two given times. For instance, calculating the time from 01:15 p.m. to 01:42 p.m. helps students practice subtraction and time conversion skills. The chapter also explores longer durations, like from 03:18 p.m. to 08:18 p.m. (which is exactly 5 hours), and shorter periods, like from 09:15 a.m. to 11:30 a.m. (which totals 2 hours and 15 minutes).

Comparing Time Taken in Activities To develop a better understanding, students are presented with a table comparing how much time three children—Raghav, Rani, and Ritu—took to paint a picture:

Name	Time Taken
Raghav	1 hour 20 minutes
Rani	2 hours 10 minutes
Ritu	1 hour 35 minutes

Students learn how to arrange these times from least to greatest and determine who was fastest and who took the longest.

12-Hour and 24-Hour Format The concept of different ways to write time is explained clearly. Students practice converting between the 12-hour format (like 02:30 p.m.) and the 24-hour format (like 14:30 hours). For example:

• 05:30 a.m. = 05:30 hours
• 08:35 hours = 08:35 a.m.
• 02:30 p.m. = 14:30 hours
• 05:30 p.m. = 17:30 hours
• 09:35 p.m. = 21:35 hours

Students also match items from two columns to reinforce the conversion between formats.

Seconds as a New Measurement Unit The chapter introduces ‘seconds’ as a smaller unit for measuring time. For example, in a 200 m-walking race, the difference in participants’ finishing times is shown in seconds, like 01:55, 01:56, and 01:57. Students learn that 1 minute is equal to 60 seconds. Understanding seconds helps detect even slight differences, especially in competitions.

Students are then asked to estimate which activities take seconds and which take minutes. Here are some examples:

• Blinking eyes – seconds
• Switching on a light – seconds
• Counting from 1 to 20 – minutes or seconds (depending on speed)
• Drinking a glass of water – minutes
• Melting an ice cube – minutes

Students are invited to list other activities that take less than a minute or just a few seconds.

Estimating and Measuring Activities The textbook encourages students to estimate how many repetitions of an activity (like blowing balloons or doing push-ups) can be done in a set time, usually one minute. They compare their estimates with actual counts. Practical questions challenge students to time themselves for quick activities, like skipping a rope in 10 seconds or writing the word “FRIEND.”

Observing Seconds using Clocks Learners are guided to observe clocks and fill in blanks related to the time taken (in seconds) for activities like getting out of bed or picking up paper. Drawing the second hand on clock faces helps visualize the passage of seconds, improving their grasp of this finer unit.

Converting Hours, Minutes, and Seconds A key part of the chapter is conversion. Students are taught that 1 hour equals 60 minutes, so to convert 2 hours to minutes, they multiply: 2 × 60 = 120 minutes. Similarly, 180 minutes is equal to 3 hours. Tables and double number lines are used to reinforce the idea:

• 1 hour 10 minutes = 70 minutes
• 2 hours 45 minutes = 165 minutes
• 3 hours 15 minutes = 195 minutes

Students also learn to convert from minutes back to hours and minutes:

• 75 minutes = 1 hour 15 minutes
• 150 minutes = 2 hours 30 minutes
• 220 minutes = 3 hours 40 minutes

Conversions between minutes and seconds are also practiced. For example, to convert 700 seconds to minutes and seconds, you divide 700 by 60:

• 700 seconds = 11 minutes 40 seconds
• 320 seconds = 5 minutes 20 seconds
• 225 seconds = 3 minutes 45 seconds

Real-Life Problem Solving The chapter asks students to solve questions about their daily schedule and time management. Problems include:

• If Jyoti goes to play at 6:15 PM and comes back after 1 hour 45 minutes, she reaches home at 8:00 PM.
• If Ragini finishes homework at 9:40 PM after 1 hour 10 minutes, she started at 8:30 PM.
• If a lunch break starts at 12:30 PM and lasts 35 minutes, it ends at 1:05 PM.

Such exercises help students apply what they've learned to practical, everyday scenarios.

Key Learnings and Teacher’s Note The teacher’s notes highlight the importance of discussing the order in which students finish activities, fostering group learning, and observing how the second hand on a clock works in relation to the minute hand. This emphasis on hands-on observation and oral problem-solving not only strengthens time concepts but also boosts critical thinking and teamwork.

By revisiting these core ideas and going through different activities, examples, and problems, students gain a solid understanding of time, its units, and practical applications in daily life.

Class 5 Maths Chapter 12 Notes – Racing Seconds: Key Points for Quick Revision

These comprehensive notes for CBSE Class 5 Maths Chapter 12 make it simple to revise topics like time measurement, conversion between hours, minutes, and seconds, and understanding the 12-hour and 24-hour formats. Key concepts like elapsed time and practical examples encourage a deeper grasp of real-life time calculations.

By using these well-structured notes, students can prepare quickly for exams and homework. Each concept is clearly explained with tables and activities, making learning about measuring time both interesting and useful for daily life.