General
UNIT 10:Time
Key unit competence
The learner should be able to tell, write and convert time appropriately.
Fun Corner
“Who has two hands but can’t wave?”
Ans: Eeeehhhh.....ahahaha....Am I not Mr. Clock?
“You are my friend, I am your friend. You can wait for me but I can never wait
for you!” Who am I?
Ans: Ahahaha...... I am Mr. Time.
Attitudes and values
Appreciate the value of time management in daily situations.
9.1 Reading and Telling TimeTime is a measure of durations of events and the intervals between them.
The short hand of the clock is called the hour hand. It measures time in hours.
If it rotates once round the clock face, then the time taken is 12 hours.
The long hand of the clock is the minute hand and it measures time in minutes.
One full rotation equals 60 minutes.
The thinnest hand is the second hand. Of the three, it rotates the fastest. Itsfull rotation equals 60 seconds.
There are two common ways of telling time:
(i) Say the hour first and then the minutes e.g.
• 6:25 = It is six twenty-five
• 8:05 = It is eight O-five (O is said like letter O)
• 9:11 = It is nine eleven
• 2:45 = It is two forty-five
(ii) Say the minutes first and then the hour e.g.
• 2:16 = It is sixteen past two
• 11:20 = It is twenty past eleven or it is eleven twenty
• 8:30 = It is half past thirty or it is eight thirty
• 8:40 = It is twenty to nine or it is eight forty
• 11:59 = It is one to twelve or it is eleven fifty-nine
• 8:51 = It is nine to nine or it is eight fifty-one.
Use of the words ‘past’ and ‘to’
• If it is 30 minutes or less after the
hour, we use the word “past”. For
example, if it is 1:16, we can say
that the time is sixteen past one.
• If it is more than 30 minutes after
the hour, we use the word “to”. For
example, if the time is 3:55, we see
that it is only 5 minutes remaining
to reach 4 o’clock. So we can say
that the time is 5 to four o’clock.
Quarter past/to and half past
15 minutes is a quarter of 60 minutes and 30 minutes is half of 60 minutes.
• When it is 15 minutes past the hour we use the words “quarter past” e.g.
6:15 = a quarter past six, 9:15 = a quarter past nine etc.
• When it is 15 minutes to the hour, we use the word “a quarter to”, e.g.
10:45 = a quarter to eleven, 4:45 = a quarter to five etc.
• When it is 30 minutes past the hour, we use the words “half past” not “half
to”. e.g. 7:30 = half past seven, 12:30 = it is half past twelve etc.
O’clock
We use o’clock, when there are no minutes. We use o’clock when the time is
exact. For example; 2:00 = two o’clock, 11:00 = eleven o’clock etc.
12:00
When it is exactly 12:00, we say it is twelve o’clock. There are 2 twelve o’clocks
in a day namely:
• Twelve o’clock midday. This is also referred to as noon.• Twelve o’clock midnight.
Solution
(a) The time is 9:40. This may be 9:40 a.m. or 9:40 p.m.
(b) The time is 5:20. It may be 5:20 a.m. early morning or 5:20 p.m. in the evening.
(c) It is one o’clock.
(d) The time is 8:40
(e) The time is 7:40(f) The time is 2:20
Exercise 10.1
1. Match the digital and analogue clocks which show the same time. Youmay use an arrow.
10.2 Writing Time Using a.m. and p.m.
Time using a.m. is ante meridian, means before midday.
Time using p.m. is post meridian, means after midday.
a.m. starts at exactly midnight at a time called 12:00 o’clock up to just before
midday (12 noon). p.m. starts at midday at a time called 12 noon and ends justbefore midnight.
Activity 10.2
Use a manilla card and plastics to form a model clock as shown below. Yourteacher will help you. Use it to show the time mentioned below.
Example 10.2
Express 9 o’clock in the morning using a.m. or p.m.
Solution
9 o’clock in the morning is 9:00 a.m.
Example 10.3
What time is a half past 5 o’clock in the evening?
Solution
A half past 5 o’clock in the evening is 5:30 p.m.
Exercise 10.2
1. Write the time using ‘a.m.’ or ‘p.m.’: 10 o’clock in the morning?
2. Express 6 o’clock in the morning as a.m. or p.m.
3. What time is half past 11 o’clock in the morning?
4. Express 2 o’clock in the afternoon using a.m. or p.m.
5. My father left Moroto at a quarter to 7 o’clock in the morning. Write thistime using a.m. or p.m.
10.3 Units of Time and Their Conversion
The standard unit of time is the second. The second is written in short as ‘s’.
Other units used to express time are minute, hour, day, week, fortnight, month,
year, decade, century and millennium, where
1 minute = 60 second(s).
1 hour = 60 minutes.
1 day = 24 hours.
1 week = 7 days.
1 fortnight = 2 weeks.
1 month = 4 weeks.
1 year = 12 months (365 days).
1 decade = 10 years.
1 century = 100 years.
1 millennium = 1000 years.
• An ordinary (common) year has 365 days and February ends on 28th.
• A leap year is a year which has 366 days and its February ends on 29th.
• 2004, 2008, 2012 were leap years and the next leap year is 2016.
• A full day has both daytime and night time, each of which lasts 12 hours.
Activity 10.3
In this class activity, you will work in groups and find out the number of
seconds that are found in:
(a) 1 minute (b) 1 hour (c) 1 day
(d) 1 week
Example 10.4
Change 4 hours to minutes.
Solution
1 hour = 60 minutes
4 hours = (4 × 60) minutes = 240 minutes.
Example 10.5
Change 180 minutes to hours.
Solution
60 minutes = 1 hour
180 minutes = 180 ÷ 60 = 3 hours
Therefore, 180 minutes = 3 hours
10.4 The Calendar
A calendar is a chart showing days, weeks and months of a particular year. A
calendar helps us to identify days and be informed of special days like Christmas,Independence Day, school term opening and closing days, birthdays, etc.
Example 10.6
Name the days of a week.
Solution
Days are: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday.
Example 10.7
Name the months of the year.
Solution
Months are: January, February, March, April, May, June, July, August,
September, October, November, December.
Activity 10.4
In this activity, you will list down all the activities you do in a day right from
the time you wake up till you go to sleep.
Activity 10.5
You will work in small groups with your classmates to finish this activity.
Carefully follow the teacher’s instructions.Study the calendar below and answer the following questions:
(a) For which year does the calendar belong?
(b) For which month of the year is the calendar?
(c) What does ‘Mo’ stand for in the calendar?
(d) On what day does the month begin?
(e) On what day does it end?
(f) How many week days does the month have?
(g) Ineza played football for 30 minutes on each weekend days of the
month. How many seconds did he spend playing football in the whole month?How many days are there in the month?
(i) On what date is the last Sunday of the month?
(j) A certain conference started on the first Monday at 9:00 a.m. and
Activity 10.6
Form yourselves into groups of 4 learners each. Study the calendar and
discuss the questions below:
(a) For which year does this calendar belong?
(b) How many months are found in a year?
(c) Which months have 30 days?
(d) Which months have 31 days?
(e) What is the last month of the year?
(f) In which month were you born?(g) In which month does Rwanda celebrate independence?
Think!!!
Charles’ mum has three children. The first is called June. The second child
is called July. What is the name of the third child?
Exercise 10.4
Using the given calendar, answer the following:
1. How many days are there in the months of January, February (not a
leap year) and March?
2. List down all months with 30 days.3. Write down all months of the year with 31 days.
10.5 Problems Involving Time
Example 10.8
Kato, is a brick layer. He makes 120 bricks every day. How many bricks
does he make in the month of January, if he works every day?
Solution
In one day, he makes 120 bricks. But, January has 31 days.
Therefore, in 31 days, he makes = 120 × 31 = 3720 bricks
Therefore, he will make 3 720 bricks.
Example 10.9
Dorah is a mother of 3 children. She has a job in town and this job enables
her to take care of her children. She goes to town everyday except on
Sundays. How many times does she go to town in the month of September,
if there are 4 Sundays in September?
Solution
September has 30 days and there are 4 Sundays.
(30 – 4) days = 26 days
Therefore, she goes to town 26 times in the month of September.
Example 10.10
It takes Aminyo 2 hours 30 minutes to travel from Kampala to her village in
Luwero. If she walks from Luwero town to her village for 1 hour 10 minutes,how much time does she spend moving from Kampala to Luwero town?
Activity 10.7
1. In groups, study the following class time table and answer the questionsgiven below:
(a) How many periods are there before break on Monday?
(b) On which day is the school’s general assembly held?
(c) How long is planned for P.E. in the whole week?
(d) Which subject is given biggest amount of time and how long?
(e) On Wednesday, the Science teacher came to class at 10:30. He
conducted an experiment in our class for 15 minutes. We then used the
remaining part of the lesson for doing a test. How long was the test?
(f) Last Friday, the community service was extended by 55 minutes
because of rain. At what time did it end?Assessment Exercise
1. Draw the hour and minute hands on the following clock faces to showthe correct times indicated:
2. Our school timekeeper always rings the bell at half past 10 o’clock in the
morning. Write this time using a.m. or p.m.
3. A match between Arsenal and Everton started at a quarter past 6 o’clock
in the evening on Saturday. Write this time in a.m. or p.m.
4. Express the following as minutes:
(a) 80 seconds (d) 150 seconds (g) 240 seconds (j) 360 seconds
(b) 70 seconds (e) 130 seconds
(c) 120 seconds (f) 480 seconds (i) 300 seconds (l) 540 seconds
5. Gloria sold pancakes every day for 2 months as follows:
September, 200 pancakes every day.
October, 100 pancakes every day.
(a) How many pancakes did she sell in September?
(b) How many pancakes did she sell in October?
(c) Find the total number of pancakes Gloria sold in the two months.
6. Bwire started washing clothes at 6:30 a.m. and stopped at 7:45 a.m.How much time did he take to wash clothes?
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