Mathematics notes, unit 5
Time
Textbook Mathematics Year 2 (DLP), Part 1 and Part 2 (one combined PDF), pages Part 2, 39–52
What this chapter covers
- You can count graduations on a clock to find minutes, and know a quarter of an hour is 15 minutes and half an hour is 30 minutes (5.1.1)
- You can say the time to 5 minutes on an analogue clock and a digital clock (5.1.2, 5.1.3)
- You can write the time in words and in numerals (5.1.2, 5.1.3)
- You can record times and activities in a table (5.1.4)
- You know 60 minutes = 1 hour and 24 hours = 1 day (5.2.1)
- You can solve simple problems about time with a clock or a timeline (5.3.1)
5.1Minutes on the clock
Look at the little lines on a clock. They are graduations. They help us count minutes.
1 graduation = 1 minute. From one number to the next number is 5 minutes.
Count in fives to find the minutes: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60.
Count in fives. The 5 times table helps you: minute hand on 7 means 7 × 5 = 35 minutes.
Figures drawn for this site; idea from Mathematics Year 2, Part 2, pp. 40-41.
How many minutes is it when the minute hand moves from 12 to 4? From 12 to 9?
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12 to 4: 4 × 5 = 20 minutes. 12 to 9: 9 × 5 = 45 minutes.
5.2Say and write the time
The short hand is the hour hand. The long hand is the minute hand. Read the hour first, then the minutes.
10:00
8:05
5:15
2:30
Digital clock
A digital clock shows the hour, then a colon, then the minutes.
(4:40)
(7:55)
| In words | In numerals |
|---|---|
| five minutes past twelve | 12:05 |
| a quarter past two | 2:15 |
| half past two (or two thirty) | 2:30 |
| eleven twenty | 11:20 |
Careful! 4:40 is "four forty" (40 minutes past four). 4:04 is only 4 minutes past four. They are not the same time.
Write in numerals: (a) five minutes past eight (b) a quarter past two. Write in words: 7:55.
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(a) 8:05 (b) 2:15 (c) Seven fifty-five.
5.3Record the time
We can write the time and the activity in a table. Put the times in order, from early to late.
| Time | Activity |
|---|---|
| 7:45 in the morning | Exercise |
| 12:00 in the afternoon | Lunch |
| 3:25 in the afternoon | Treasure hunt |
Write morning, afternoon, evening or night after the time so that we know which part of the day it is.
In the table, what activity is at 12:00 in the afternoon?
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Lunch.
5.4Hours and days
60 minutes = 1 hour
12 hours + 12 hours = 24 hours = 1 day
12 hours + 12 hours = 24 hours = 1 day
- The minute hand moves 1 complete circle in 1 hour.
- The hour hand moves 2 complete circles in 1 day (12 hours each).
- 12:00 in the day is noon. 12:00 in the night is midnight.
- Quarter of an hour = 15 minutes. Half an hour = 30 minutes.
1 hour is 60 minutes, not 100 minutes.
1 hour = ___ minutes. 1 day = ___ hours. Half an hour = ___ minutes.
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60 minutes, 24 hours, 30 minutes.
5.5Solve problems about time
Example
Alex arrived at school when the hour hand was just after 7 and the minute hand showed 4. What time did he arrive?4 × 5 = 20 minutes. He arrived at 7:20 in the morning.
Example
Dinner started 25 minutes after 8:00 in the evening. Count on in fives from 12: 5, 10, 15, 20, 25. Stop at 5. Dinner started at 8:25 in the evening.Example
A story started at 2 o'clock and went on for 1 hour. The minute hand moves 1 complete circle. It ended at 3 o'clock.Draw a clock or a timeline. Count in fives for minutes.
A chess game started at 4:00 in the afternoon. When it ended the minute hand was on 8. What time did it end?
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8 × 5 = 40 minutes, so it ended at 4:40 in the afternoon.
Summary
- 1 graduation = 1 minute. From one number to the next is 5 minutes: count in fives.
- Quarter of an hour = 15 minutes. Half an hour = 30 minutes. 1 hour = 60 minutes. 1 day = 24 hours.
- Read the hour first, then the minutes. 4:40 is "four forty"; 4:04 is only 4 minutes past four.
- Write morning, afternoon, evening or night after the time.