Time - Sub Topics

  • What is Time?
  • Measurement of Time
  • What are the Units of Time?
  • Conversion of One Unit to Another Unit
  • Formats of time
  • Solved Questions on Time
  • In this chapter, we’ll explore the concept of time, what clocks are and how we measure time. Time is something we all know about and use every day. It helps us understand when things happen like waking up in the morning, going to school or having lunch. Time is all around us and it's essential for organizing our lives.

    What is Time?

    Time is the period during which everything happens. It is a fascinating idea that shapes our everyday activities from rising in the morning to sleeping at night. Time plays a crucial role in scheduling our day and comprehending when various events take place.

    We often measure time using clocks. Clocks can be found in our homes, schools and even on our devices like phones and computers. They have hands that move around in a circle, showing us the hours and minutes.

    Measurement of Time

    Time is measured using a clock. On the clock face, there are 12 numbers that help us tell the time. A clock has three hands:

    → The big hand shows the minutes.

    → The small hand shows the hours.

    → The thin hand shows the seconds.


    In a digital clock, the numbers are used to display the hours, minutes and seconds, like this:


    Now, let's practice reading a clock:


    This is how the minute hand's motion shows different times within a single hour.

    Quarters of Time

    A “quarter of time” is a concept related to fractional time. When we say “quarter of the time”, we are talking about dividing time into 4 equal parts or “quarters”. Each “quarter” can be represented as:


    Units of Time

    Years, months, weeks, days, hours, minutes and seconds are all units of time. Among these units, a year is the largest and a second is the smallest unit of time.

    Conversion of one unit to another unit

    Converting from one unit of time to another involves the following:

    → 1 year = 12 months

    For example: 5 years = 5 × 12 months
                                     = 60 months


    a. A month can have 28, 29, 30 or 31 days depending on the month.
    b. One year has 365 days.
    c. A leap year has 366 days.
    d. In a standard year, there are 28 days in February while in a leap year, there are 29 days in February.
    e. In a standard year, there are 52 weeks plus one extra day while in a leap year, there are 52 weeks plus two extra days.

    → 1 week is equal to 7 days.

    For example: 5 weeks = 5 × 7 days 

    = 35 days

    → One day is equal to 24 hours.

    For example, 5 days = 5 × 24 hours 

    = 120 hours

    → 1 hour is equal to 60 minutes.

    For example, 3 hours = 3 × 60 minutes

    = 180 minutes

    → 1 minute is equal to 60 seconds.

    For example, 4 minutes = 4 × 60 seconds

    = 240 seconds

    → 1 hour is equal to 3600 seconds.

    For example: 2 hours = 2 × 3600 seconds

    = 7200 seconds

    Example: Fill in the blanks:7 hours is equal to ________ seconds.

    a) 20200 seconds
    b) 25200 seconds
    c) 30200 seconds
    d) 35200 seconds

    Answer: b) 25200 seconds

    Explanation: 1 hour = 3600 seconds
    7 hours = 7 3600 seconds
                = 25200 seconds

    7 hours is equal to 25200 seconds.

    Formats of Time

    There are two formats of time: the 12-hour format and the 24-hour format. Typically, we mostly use the 12-hour clock for timekeeping in our daily lives. However, the 24-hour clock is preferred by the railways, airlines and news media for precise time notation.

    It's important to know the difference between 12-hour time and 24-hour time. Here's a quick guide on how to know the difference.

    12-Hour Format: In the 12-hour format, we divide the day into two segments:

    → "Ante Meridiem" (AM) covers the time from midnight (12:00 AM) to noon (12:00 PM).
    → "Post Meridiem" (PM) covers the time from noon (12:00 PM) to midnight (12:00 AM).

    The day's cycle is illustrated as follows:

    This format is commonly used on traditional clocks and watches. To express time in the 12-hour format, we use numbers from 1 to 12, followed by "AM" or "PM" to indicate whether it's morning, afternoon, evening or night. The 12-hour format is shown as:


    24-Hour Format: The 24-hour format is also known as the international time format that divides the entire day into 24 hours, eliminating the need for "AM" or "PM."

    → The hours range from 00:00 (midnight) to 23:59 (just before the next midnight).
    → It offers a continuous time count without switching between AM and PM. The 24-hour format is shown as:


    For example, 9:45 AM in the 12-hour format equals 09:45 in the 24-hour format and 9:45 PM in the 12-hour format equals 21:45 in the 24-hour format.

    Let's explore some terms related to days:

    → "Today" refers to the current day.
    → "Yesterday" is the day that occurred before today.
    → "Tomorrow" is the day that occurred after today.

    We can better grasp these concepts with an example:


    Example: If today is Thursday, which day will be the day after tomorrow?

    a) Sunday
    b) Friday
    c) Thursday
    d) Saturday 

    Answer: d) Saturday

    Explanation: If today is Thursday, then tomorrow will be Friday. The day after tomorrow will be Saturday. The days are marked in the figure below:


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