Time Textbook

Time Let’s Learn!

Seconds 11 12 1 10 2 3 9 4 8 7 6 5

1

This is the second hand.

5.30

11 12 1 10 2 3 9 4 8 7 6 5

11 12 1 10 2 3 9 4 8 7 6 5

11 12 1 10 2 3 9 4 8 7 6 5

10 seconds later

35 seconds later

60 seconds later

One complete turn round the clock by the second hand is equal to 60 seconds.

60 seconds = 1 minute

2

Meng Choon, what can you do in 1 s?

The second is another unit of measurement for time. We use s to stand for seconds.

I can say, one thousand and one!

Wow! That was fast!

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3

Carry out these activities.

Do they take 1 s, more than 1 s or less than 1 s?

Activity

1s

More than 1 s

Less than 1 s

Say “thirty-four�

Blink once Raise your hand Raise your hand and bring it down Nod twice Say your full name Say the National Pledge

4

Raj walks from one end of a classroom to the other. Mr Tang times him.

Raj takes 10 s to walk from one end of the classroom to the other.

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5

Play this game!

Players: 2 You need: • 2 containers, X and Y. • 30 marbles • stopwatch

1

Player A puts 10 marbles into Container X.

2

Then he takes the marbles one at a time from Container X and puts them into Container Y as fast as he can.

3

Player B draws up a table as shown below. He estimates the time Player A will take to transfer the 10 marbles. He writes down the estimates in the table.

4

Then Player B uses a stopwatch and times Player A as Player A transfers the 10 marbles. Player B records the actual time taken in the table.

5

Players A and B repeat steps 1 to 4 for transferring 20 marbles and 30 marbles.

6

The players then exchange places and repeat the above activity.

Player A Number of marbles transferred

Time taken in seconds to transfer marbles Estimate

Actual

10 20 30 Total time taken

I win because my estimates are closer to the actual time than yours!

I win because I am the fastest!

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6 The clock shows 8.20.

11 12 1 10 2 3 9 4 8 7 6 5

11 12 1 10 2 3 9 4 8 7 6 5

After 60 s, the time is

11 12 1 10 2 3 9 4 8 7 6 5

7

.

Another 60 s later, the time . is

Find the duration.

11 12 1 10 2 3 9 4 8 7 6 5 3.30

11 12 1 10 2 3 9 4 8 7 6 5 s later

11 12 1 10 2 3 9 4 8 7 6 5 s later

11 12 1 10 2 3 9 4 8 7 6 5 s later

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8

Your teacher will give you the clock faces. Draw the missing minute and/or second hand(s) on each clock face. Then find out the time.

11 12 1 10 2 3 9 4 8 7 6 5

after 50 s

a.m.

7.15 a.m.

11 12 1 10 2 3 9 4 8 7 6 5

after 25 s

a.m.

9

11 12 1 10 2 3 9 4 8 7 6 5 after 45 s

11 12 1 10 2 3 9 4 8 7 6 5 a.m.

Carry out this activity.

Your teacher will give you 60 s to make a paper aeroplane. a

Were you able to make the aeroplane within 60 s?

Next, throw the paper aeroplane into the air and count how long it can stay in the air.

Work in pairs to count in seconds.

1 thousand, 2 thousand, One of you counts using “thousands” like this: 3 thousand, 4 thousand...

Each “thousand” stands for 1 second.

The other uses a stopwatch. b

How many seconds did the paper aeroplane stay in the air?

Compare the answers.

WB 4B, p 79 Practice 1

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Let’s Learn!

24-Hour Clock 1

Nicole gets up at the same time every day.

Look at the time on the clock.

It is 6.30 in the morning. We write it as 6.30 a.m.

We read it as six thirty a.m.

We can write the time in another way.

We can write it as 06 30.

We read it as zero six thirty hours.

6.30 a.m. is a way of showing time using the 12-hour clock.

06 30 is a way of showing time using the 24-hour clock.

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2

3

School starts at 7.40 in the morning every day. a

Using the 12-hour clock, we write the time as

b

Using the 24-hour clock, we write the time as

Write the following times using the 24-hour clock. a

4

9.15 a.m.

b 11.05 a.m.

Write the following times using the 12-hour clock. a

5

.

08 45

b 10 24

School ends at 1.45 in the afternoon every day.

We write the time as 1.45 p.m.

1.45 p.m. is expressing the time using the 12-hour clock.

How do we express 1.45 p.m. using the 24-hour clock?

12 h

12 h

midnight 00 00

noon 1.45 p.m.

midnight

12 00

00 00

12 h

13 45

1 h 45 min

We can also say that school ends at 13 45 every day.

Home Maths

12 + 1 =13

We read 13 45 as thirteen forty-five hours.

Explain to your child that in the 24-hour clock, midnight is represented by 00 00.

In the time line for 5 , explain to your child: noon 1.00 p.m.

1.45 p.m. 2.00 p.m.

To convert 1.45 p.m. to 13 45

12 00

13 00 1h

13 45 14 00 45 min 87

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6

Nicole goes to bed at 10.00 every night. We write the time as 10.00 p.m.

midnight

noon

00 00

12 00

10.00 p.m. midnight 22 00 00 00

12 hours

10 + 12 = 22

10 hours

22 00 is another way of showing 10.00 p.m.

Nicole goes to bed at 22 00 every night.

We read 22 00 as twenty-two hundred hours.

7

Write the following times using the 24-hour clock. a

8.30 p.m.

a Add

to

.

b

11.15 p.m.

b Add

to

.

Home Maths

Help your child to draw a time line for a 12-hour clock and a 24-hour clock (a guide on how to do this is given below). Then ask your child to tell the time using the time line for the 24-hour and 12-hour clocks.

24-hour clock

00 00

01 00

11 00

12 00

13 00

23 00

12-hour clock

midnight

1.00 a.m.

11.00 a.m.

noon

1.00 p.m.

11.00 midnight p.m.

00 00

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8

What is 21 35 using the 12-hour clock?

21 – 12 = 9

12 hours midnight

noon

9.35 p.m. midnight

00 00

12 00

21 35 00 00 9 h 35 min

21 35 is the same as 9.35 p.m.

2 h 25 min

Using the 12-hour clock, 21 35 is 9.35 p.m.

9

10

11

Express the following times using the 24-hour clock. a

8.50 a.m.

b

8.50 p.m.

c

6.30 a.m.

d

9.15 a.m.

e

7.40 p.m.

f

11.25 p.m.

Express the following times using the 12-hour clock. a

07 35

b

19 35

c

08 20

d

12 30

e

18 40

f

21 35

Remember! In the 12-hour clock time, a.m. or p.m. must be stated. Why?

Marianne started ironing her uniform at 16 00. She finished ironing at 16 35.

How long did Marianne take to iron her uniform? ?

Draw a time line to show the time.

16 00

16 35

Marianne took 35 min to iron her uniform.

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12

Hamidah had her dinner at 18 00. She finished her dinner 25 minutes later.

At what time did Hamidah finish her dinner?

Count forward.

25 min

?

18 00

Hamidah finished her dinner at 18 25.

13

Swee Lian ended her piano lesson at 15 45. Her lesson lasted 40 minutes.

At what time did Swee Lian begin her piano lesson?

40 min Count backwards. ?

15 45

Swee Lian began her piano lesson at 15 05.

14

Ben left his school at 19 45. He took a bus and reached home 50 minutes later. At what time did Ben reach home?

15 min

15

35 min

50 35

19 45

?

20 00

Ben reached home at 20 35.

15

Jaya began her English lesson at 12 25. She finished the lesson 45 minutes later. At what time did Jaya finish her English lesson? min

min

?

45

12 25

?

13 00 ?

Jaya finished her English lesson at

.

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16

Mala baked a cake in an oven for 50 minutes. She removed the cake from the oven at 10 15. At what time did Mala start baking?

50 min = 15 min +

15

min

50

min

?

09 00

10 00

Count backwards.

?

?

19 30 19 45 20 00

21 00 21 20 21 30

The concert lasted

h

min.

Diana took 40 minutes to make some pineapple tarts for Chinese New Year. She started baking at 11 45. At what time did she finish baking?

11 30

11 45

?

12 00

She finished baking at

19

11 00

A concert at the Esplanade started at 19 45. It ended at 21 20. How long did the concert last? ?

18

10 15

.

Mala started baking at 17

?

15 min

.

Shirley took the MRT at Sembawang station and reached Newton station 26 minutes later. She arrived at Newton station at 11 20. At what time did she board the train at Sembawang station?

10 30

?

She boarded the train at

11 00

11 20

11 30

.

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20

David’s Art lesson started at 15 30. The lesson lasted 1 h 10 min. At what time did the Art lesson end?

Method 1

15 00

10 min

1h

16 30 ?

16 00

15 30

17 00

10 minutes after 16 30 is 16 40.

Method 2 1 h 10 min = 70 min = 30 min + 40 min 40 min

30 min

15 00

?

16 00

15 30

17 00

40 minutes after 16 00 is 16 40.

The Art lesson ended at 16 40.

21

A movie ended at 22 05. It lasted 2 h 25 min. At what time did the movie start?

Method 1 25 min

?

1h

1h

20 05

21 05

22 05

Method 2 20 min

?

1h

20 00

The movie started at

Home Maths

1h

21 00

5 min

22 00 22 05

.

At the bus interchange, point out the departure times of various buses. Ask your child how the times are read using the 24-hour clock. Then ask him what the times are using the 12-hour clock.

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22

A plane left Changi Airport at 13 45 and landed in Kuching, Sarawak at 15 10 on the same day. How long was the journey? ? min

? min

13 45

Draw a time line to show the time taken.

? min

15 00 15 10

14 00

From

To

13 45

14 00

15 min

14 00

15 00

60 min = 1 h

15 00

15 10

10 min

Total time

Time taken

1 h 25 min

The journey was 1 h 25 min long.

23

Mr Taha started jogging at 17 45 and finished at 19 15. For how long did he jog? min

17 45

min

min

18 00

19 00

From

To

17 45

18 00

18 00

19 00

19 00

19 15

19 15

Time taken

Total time He jogged for

h

min.

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24

Sarina went to the Fantastic Four Furries concert on Saturday. The concert ended at 23 30. Sarina reached home at 00 15. a

Did she reach home on the same day?

b

How long did she take to reach home? ? min

23 30

a

b

? min

00 00

00 15

00 30

Midnight is written as 00 00.

00 15 is after midnight. Sarina reached home on Sunday!

From 23 30 00 00 (beginning of Sunday)

To 00 00 (end of Saturday)

Time taken 30 min

00 15

15 min

Total time

45 min

Sarina took 45 min to get home.

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25

A plane departed Singapore at 22 50 on Wednesday. It landed in Bangkok at 01 20. How long was the flight? Did it reach Bangkok on the same day or the next day? ?

?

22 00

?

22 50 23 00

00 00

From

To

22 50

23 00

23 00

00 00

00 00

01 00

01 00

01 20

The flight was

h

It reached Bangkok the

?

01 00 01 20

02 00

Time taken

min long. day.

Do you know where Bangkok is? Look at the world map to find out!

Ma t hs Jo urn al

Using the 24-hour clock, make a diary of your activities on a school day from the time you get up to the time you go to bed.

Example

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26

Carry out this activity.

Work in pairs. a

Each of you will use the following to write a word problem.

20 35 began

1 h 45 min finished

Eugene what time

homework he took

You and your partner exchange word problems and solve them. b

The table below shows the departure times of various planes from Changi Airport and their arrival times at various destinations in Malaysia.

Destination

Time of departure from Singapore

Expected time of arrival at destination

SQ192

Penang

08 05

09 30

SQ5638

Kuching

13 25

14 50

SQ112

Kuala Lumpur

15 10

16 05

MH630

Kota Kinabalu

17 05

19 30

MI368

Langkawi

18 35

20 00

Flight number

1

How long does it take to fly from Singapore to Penang?

2

June took the SQ112 flight from Singapore to Kuala Lumpur. June’s mother took a later plane and arrived in Kuala Lumpur at 21 35. Her flight took the same amount of time as June’s. At what time did the plane that her mother took depart from Changi Airport?

3

Mr Bala took MH630 to Kota Kinabalu. His flight was delayed for 45 minutes. At what time did Mr Bala finally arrive in Kota Kinabalu?

4

Rahman and his friends were on the flight to Kuching when they were told that due to bad weather, they would be arriving in Kuching later than expected. They finally arrived in Kuching at 15 15. How long was the journey?

WB 4B, p 81 Practice 2

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Maths Jo urnal

Put a tick (✓) to show which part(s) of this chapter you like most.

Put a cross (✗) to show which part(s) of this chapter you find difficult.

24-Hour Clock: a

Change time from 12-hour clock to 24-hour clock.

b

Change time from 24-hour clock to 12-hour clock.

c

Find duration.

d

Find end time.

e

Find start time.

Put On Your Thinking Caps!

Mr Lee alighted from a MRT train at 00 30 on New Year’s Day. His ride was 55 minutes long. At what time did he board the MRT train? What day was it?

23 00

Mr Lee boarded the MRT train at

?

00 00

. It was

00 30

.

WB 4B, p 87 Challenging Practice WB 4B, p 88 Problem Solving

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