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Time formats


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Last updated 26 October 2012 15:28 by NZTecAdmin
Time formats (PDF, 35 KB)

Measurement progression, 4th step

In this activity, the learners become familiar with expressing time in each of its three forms: analogue, 12 hour, and 24-hour digital.

The teaching points

  • There are 60 minutes in one hour. There are three ways of expressing time:

    Image of table of three expressions of time.

  • On an analogue clock, there is a hand to indicate the hours and another to indicate the minutes. One circuit of the minute hand is 60 minutes or one hour. Each division is 5 minutes. Time is expressed as minutes past the hour until 30 minutes past and then is usually expressed as minutes to the hour. 15 minutes past the hour is quarter of the circuit and is often called quarter past the hour. 30 minutes past the hour is half the circuit and is often called half past the hour. 15 minutes to the hour is also called quarter to the hour. There is nothing to indicate whether it is morning or afternoon.
  • On digital clocks, time is expressed as hours: minutes. The minutes are always expressed as past the hour, counting on from :00 until :59. There are still 60 minutes in the hour so :00 is o’clock and :30 is still half past the hour.
  • 24-hour time is expressed as hours:minutes (or without a gap). The hours are expressed from 00 to 23 (00:00 being midnight). There is no confusion between morning or afternoon.
  • Discuss with the learners the fact that morning or afternoon is usually indicated by “am” (from the Latin ante meridiem/meridian – before noon) or “pm” (post meridiem/meridian – after noon).

Resources

  • A selection of analogue clocks and watches and digital clocks and watches, some of which show 24-hour time.

The guided teaching and learning sequence

1. Begin by brainstorming the words used to talk about time and recording these on the board. For example: hours, minutes, seconds, 10 to or past, quarter to or past, half past, o’clock, two fifty.

2. Explain that there are three different ways in which clocks show time and ask the learners if they can describe them.

3. Show the learners an analogue clock and ask the following questions. Record key points on the board.

“How much time is one complete circuit of the clock?”
“Give this time in two different units” (1 hour, 60 minutes)
“How much time in one segment of the clock?” (5 minutes)

4. Set the clock to 10 past 1 and ask the following questions:

“What is the time?”
“Are there other ways in which this can be said?” (10 past 1, one ten)
“How do you know it is 10 minutes past?” (two segments of 5 minutes each)

5. Set the clock to half past 2 and ask:

“What is the time?” “Are there other ways in which this can be said?” (half past 2, two thirty)
“How do you know?” (half way round the clock, whole clock 60 minutes, half is 30, six segments of 5 minutes)

6. Ask for a volunteer to set the clock to other times when fractions are used (quarter past, quarter to) and to explain why they are used (a complete circuit of the clock represents one hour, at quarter past the hour one quarter of that circuit has been completed, at quarter to the hour one quarter of the circuit remains to go).

7. Divide the learners into groups and give each group two digital clocks, one with and one without 24-hour time. Ask the learners to identify similarities to and differences from an analogue clock.

Listen for and reinforce one hour is 60 minutes, the first two digits express hours, the second two minutes, time is always reported in minutes past the hour, the hours run from 00 to 12 or 00 to 23 (the latter indicating the difference between morning and afternoon), midnight is 00.

Follow-up activity

Divide the learners into groups of three with each learner in the group taking on the role of analogue time, digital time or 24-hour time. One names a time, and the other two give it in their format. Encourage the learners to change around to practise all forms of time.

When they are familiar with the formats, get them to ask each other questions, such as:

“What is the time in half an hour?”
“What will the time be in 11 hours?”
“What was the time 2 hours ago?”
“What will be the time in 35 minutes?”
and to give the answer in all formats.

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