Mathematics -- Class 4

Topic: Time (Reading, Duration, Conversion, and 24-Hour Clock)
Name: ____________________________Class: 4Date: ________________
Learning Objectives
A Friendly Introduction

In Class 3, you learned to read time using hours and half hours. You also learned about a.m. and p.m. Now in Class 4, we will read time more precisely -- to every 5 minutes!

Think about your school day. The bell rings at 7:45 a.m. and the first period ends at 8:25 a.m. How long was the period? We will learn to find such durations. We will also learn the 24-hour clock used in railways and airports across India.

Reading Time to 5 Minutes

The minute hand moves from one number to the next in 5 minutes. Count by 5s from 12 to read the minutes.

Quarter past = 15 minutes past the hour. Quarter to = 15 minutes before the next hour.

Example 1:

If the hour hand is between 3 and 4, and the minute hand is on 3, the time is 3:15 or quarter past 3.

Example 2:

If the hour hand is near 9 and the minute hand is on 9, the time is 8:45 or quarter to 9.

Think: The minute hand is on 7. How many minutes past the hour is it?

Finding Duration

Duration is the amount of time between a start time and an end time. Count forward from the start time to the end time.

Example 3: A cricket match starts at 2:30 p.m. and ends at 5:15 p.m. How long was the match?

From 2:30 to 5:00 = 2 hours 30 minutes.

From 5:00 to 5:15 = 15 minutes.

Total duration = 2 hours 45 minutes.

Example 4: Meena starts her homework at 4:10 p.m. and finishes at 5:00 p.m. How long did she study?

From 4:10 to 5:00 = 50 minutes.

Converting Hours and Minutes

1 hour = 60 minutes. To convert hours to minutes, multiply by 60. To convert minutes to hours, divide by 60.

Example 5: Convert 3 hours to minutes.

3 x 60 = 180 minutes.

Example 6: Convert 150 minutes to hours and minutes.

150 / 60 = 2 hours and 30 minutes (since 2 x 60 = 120, and 150 - 120 = 30).

Answer: 2 hours 30 minutes.

The 24-Hour Clock

In the 24-hour clock, we do not use a.m. or p.m. The hours go from 00:00 (midnight) to 23:59.

For times after 12 noon, add 12 to the hour. For example, 3:00 p.m. = 15:00 hours.

12-Hour Clock24-Hour Clock
12:00 midnight00:00
6:30 a.m.06:30
12:00 noon12:00
4:15 p.m.16:15
9:45 p.m.21:45

Think: The Rajdhani Express departs at 16:50. What time is that in the 12-hour clock?

Key Words
WordMeaning
DurationThe amount of time from start to end
Quarter Past15 minutes after the hour
Quarter To15 minutes before the next hour
24-Hour ClockA time system that counts hours from 0 to 23
CalendarA chart showing days, weeks, and months of a year

Mathematics -- Class 4 (continued)

Topic: Time -- Key Points and Practice
Calendar Problems

Remember: 1 year = 12 months = 365 days (366 in a leap year). 1 week = 7 days.

Months with 31 days: January, March, May, July, August, October, December.

Months with 30 days: April, June, September, November. February has 28 or 29 days.

Example 7: How many days are there from 10th March to 25th March?

Count from 10th to 25th: 25 - 10 = 15 days.

Key Points to Remember
Practice Questions

A. Fill in the Blanks

  1. Quarter past 6 means .
  2. Quarter to 10 means .
  3. 2 hours = minutes.
  4. 240 minutes = hours.
  5. 5:30 p.m. in 24-hour clock = .

B. Find the Duration

  1. Start: 8:15 a.m., End: 10:45 a.m. Duration =
  2. Start: 3:00 p.m., End: 5:30 p.m. Duration =
  3. Start: 11:20 a.m., End: 1:05 p.m. Duration =

C. Convert to 24-Hour Clock

  1. 7:00 a.m. =
  2. 2:45 p.m. =
  3. 11:30 p.m. =
  4. 12:15 a.m. =

D. Multiple Choice Questions

  1. How many minutes are there in 3 hours 20 minutes?
    (a) 180(b) 200(c) 320(d) 150
  2. What is 18:00 in the 12-hour clock?
    (a) 6:00 a.m.(b) 8:00 p.m.(c) 6:00 p.m.(d) 8:00 a.m.
  3. How many days are there in the month of November?
    (a) 28(b) 30(c) 31(d) 29

E. Word Problems

  1. A train departs from Delhi at 14:30 and arrives in Jaipur at 19:15. How long is the journey?
  2. Rohan's school starts at 7:45 a.m. and ends at 1:30 p.m. How many hours and minutes is his school day?
  3. Sita's birthday is on 18th April. Her friend's birthday is on 5th May. How many days are between the two birthdays?
Fun Activity -- My Day in 24-Hour Time

Write the time of each activity in both 12-hour and 24-hour format.

Activity12-Hour Time24-Hour Time
Wake up
Reach school
Lunch
Play time
Go to bed