Primary 5 Mathematics Holistic Decimals.pptx

© 2017 Marshall Cavendish Education Pte Ltd
Primary 5 Mathematics
My Pals Are Here, Book B, Chapter 9: Decimals
Shaping Maths, Book B, Unit 1: Decimals; Unit 2: Four Operations of Decimals
Decimals

Chapter Learning Outcomes
• Multiplying by 10, 100, 1000 and their multiples
• Dividing by 10, 100, 1000 and their multiples
• Converting measurements
• Solving word problems

Multiplying by 10, 100, 1000 and Their Multiples
a) What is 4.003 × 10?
4.003 × 10 = 40.03
× 10
Tens Ones Tenths Hundredths Thousandths
4 0 0 3
4 0 0 3

b) What is 5.2 × 10?
5.2 × 10 = 52
What pattern
do you notice?
× 10
5 2
5 2

Let’s Try!
Multiply.
a) 0.712 × 10 =
b) 9.35 × 10 =
c) 10 × 17.4 =
d) 10 × 22.08 =
7.12
93.5
174
220.8

Let’s Try!
Find the missing numbers.
a) 0.006 × = 0.06
b) × 8.74 = 87.4
c) 10 × = 320.7
d) × 10 = 80.08
10
10
32.07
8.008

What is 1.203 × 30?
Method 1
1.203 × 30 = 1.203 × 10 × 3
= 12.03 × 3
= 36.09
× 10 × 3
1.203 × 10 = 12.03 12.03 × 3 = 36.09

What is 1.203 × 30?
Method 2
1.203 × 30 = 1.203 × 3 × 10
= 3.609 × 10
= 36.09
× 3 × 10
1.203 × 3 = 3.609 3.609 × 10 = 36.09

Let’s Try!
Multiply.
a) 0.107 × 30 =
b) 60 × 4.81 =
c) 2.9 × 90 =
d) 50 × 12.304 =
3.21
288.6
261
615.2

a) What is 0.32 × 100?
0.32 × 100 = 32
× 100
3 2
3 2

What pattern
do you notice?
b) What is 3.401 × 100?
3.401 × 100 = 340.1
× 100
Hundreds Tens Ones
Tenth
s
Hundredths Thousandths
3 4 0 1
3 4 0 1

Let’s Try!
Multiply.
a) 0.19 × 100 =
b) 2.8 × 100 =
c) 100 × 4.08 =
d) 100 × 7.305 =
19
280
408
730.5

Let’s Try!
a) 3.96 × = 396
b) × 51.2 = 5120
c) 100 × = 3700.6
d) × 100 = 4009
100
100
37.006
40.09

What is 1.402 × 200?
Method 1
1.402 × 200 = 1.402 × 100 × 2
= 140.2 × 2
= 280.4
× 100 × 2
1.402 × 100 = 140.2 140.2 × 2 = 280.4

What is 1.402 × 200?
Method 2
1.402 × 200 = 1.402 × 2 × 100
= 2.804 × 100
= 280.4
× 2 × 100
1.402 × 2 = 2.804 2.804 × 100 = 280.4

Let’s Try!
Multiply.
a) 0.066 × 700 =
b) 400 × 2.8 =
c) 9.03 × 800 =
d) 300 × 15.307 =
46.2
1120
7224
4592.1

a) What is 0.015 × 1000?
0.015 × 1000 = 15
× 1000
Tens Ones
Tenth
s
1 5
1 5

What pattern
do you notice?
b) What is 0.35 × 1000?
0.35 × 1000 = 350
Hundreds Tens Ones
Tenth
s
Hundredths
3 5
3 5
× 1000

Let’s Try!
Multiply.
a) 0.55 × 1000 =
b) 3.009 × 1000 =
c) 1000 × 5.2 =
d) 1000 × 20.01 =
550
3009
5200
20 010

Let’s Try!
a) 4.76 × = 4760
b) × 2.5 = 2500
c) 1000 × = 3901
d) × 1000 = 10 080
1000
1000
3.901
10.08

What is 3.012 × 3000?
Method 1
3.012 × 3000 = 3.012 × 1000 × 3
= 3012 × 3
= 9036
× 1000 × 3
3.012 × 1000 = 3012 3012 × 3 = 9036

What is 3.012 × 3000?
Method 2
3.012 × 3000 = 3.012 × 3 × 1000
= 9.036 × 1000
= 9036
× 3 × 1000
3.012 × 3 = 9.036 9.036 × 1000 = 9036

Let’s Try!
Multiply.
a) 0.504 × 6000 =
b) 4000 × 3.18 =
c) 11.006 × 5000 =
d) 8000 × 20.9 =
3024
12 720
55 030
167 200

Dividing by 10, 100, 1000 and Their Multiples
a) What is 4.05 ÷ 10?
4.05 ÷ 10 = 0.405
÷ 10
Ones Tenths Hundredths Thousandths
4 0 5
4 0 5

What pattern
do you notice?
b) What is 20.5 ÷ 10?
20.5 ÷ 10 = 2.05
÷ 10
2 0 5
2 0 5

Let’s Try!
Divide.
a) 53 ÷ 10 =
b) 34.1 ÷ 10 =
c) 20.08 ÷ 10 =
d) 17.96 ÷ 10 =
5.3
3.41
2.008
1.796

Let’s Try!
a) 0.25 ÷ = 0.025
b) 3.9 ÷ = 0.39
c) ÷ 10 = 8.4
d) ÷ 10 = 7.06
10
10
84
70.6

What is 8.26 ÷ 20?
Method 1
8.26 ÷ 20 = 8.26 ÷ 10 ÷ 2
= 0.826 ÷ 2
= 0.413
÷ 10 ÷ 2
8.26 ÷ 10 = 0.826 0.826 ÷ 2 = 0.413

What is 8.26 ÷ 20?
Method 2
8.26 ÷ 20 = 8.26 ÷ 2 ÷ 10
= 4.13 ÷ 10
= 0.413
÷ 2 ÷ 10
8.26 ÷ 2 = 4.13 4.13 ÷ 10 = 0.413

Let’s Try!
Divide.
a) 24 ÷ 80 =
b) 18.6 ÷ 30 =
c) 2.04 ÷ 60 =
d) 0.96 ÷ 40 =
0.3
0.62
0.034
0.024

a) What is 3.2 ÷ 100?
3.2 ÷ 100 = 0.032
÷ 100
Ones Tenths Hundredths Thousandths
3 2
3 2

What pattern
do you notice?
b) What is 14 ÷ 100?
14 ÷ 100 = 0.14
÷ 100
Tens Ones Tenths Hundredths
1 4
1 4

Let’s Try!
Divide.
a) 17 ÷ 100 =
b) 30 ÷ 100 =
c) 9.5 ÷ 100 =
d) 400.6 ÷ 100 =
0.17
0.3
0.095
4.006

Let’s Try!
a) 45 ÷ = 0.45
b) 8.3 ÷ = 0.083
c) ÷ 100 = 0.5
d) ÷ 100 = 7.103
100
100
50
710.3

What is 40.2 ÷ 200?
Method 1
40.2 ÷ 200 = 40.2 ÷ 100 ÷ 2
= 0.402 ÷ 2
= 0.201
÷ 100 ÷ 2
40.2 ÷ 100 = 0.402 0.402 ÷ 2 = 0.201

What is 40.2 ÷ 200?
Method 2
40.2 ÷ 200 = 40.2 ÷ 2 ÷ 100
= 20.1 ÷ 100
= 0.201
÷ 2 ÷ 100
40.2 ÷ 2 = 20.1 20.1 ÷ 100 = 0.201

Let’s Try!
Divide.
a) 963 ÷ 300 =
b) 56.8 ÷ 400 =
c) 850 ÷ 500 =
d) 60.9 ÷ 700 =
3.21
0.142
1.7
0.087

a) What is 301 ÷ 1000?
301 ÷ 1000 = 0.301
÷ 1000
Hundreds Tens Ones
Tenth
s
3 0 1
3 0 1

What pattern
do you notice?
b) What is 12 ÷ 1000?
12 ÷ 1000 = 0.012
÷ 1000
1 2
1 2

Let’s Try!
Divide.
a) 487 ÷ 1000 =
b) 9130 ÷ 1000 =
c) 8500 ÷ 1000 =
d) 30 002 ÷ 1000 =
0.487
9.13
8.5
30.002

Let’s Try!
a) 138 ÷ = 0.138
b) 6475 ÷ = 6.475
c) ÷ 1000 = 2.19
d) ÷ 1000 = 8.6
1000
1000
2190
8600

What is 26 ÷ 2000?
Method 1
26 ÷ 2000 = 26 ÷ 1000 ÷ 2
= 0.026 ÷ 2
= 0.013
÷
1000
÷ 2
26 ÷ 1000 = 0.026 0.026 ÷ 2 = 0.013

What is 26 ÷ 2000?
Method 2
26 ÷ 2000 = 26 ÷ 2 ÷ 1000
= 13 ÷ 1000
= 0.013
÷ 2 ÷ 1000
26 ÷ 2 = 13 13 ÷ 1000 = 0.013

Let’s Try!
Divide.
a) 804 ÷ 4000 =
b) 9128 ÷ 7000 =
c) 7200 ÷ 9000 =
d) 30 400 ÷ 8000 =
0.201
1.304
0.8
3.8

a) Convert 5.4 m to centimetres.
1 m = 100 cm
5.4 m = 5.4 × 100
= 540 cm
b) Convert 3.6 kg to grams.
1 kg = 1000 g
3.6 kg = 3.6 × 1000
= 3600 g
Converting Measurements
5.4
3.6

c) Convert 9.03 km to metres.
1 km = 1000 m
9.03 km = 9.03 × 1000
= 9030 m
d) Convert 7.008 l to millilitres.
1 l = 1000 ml
7.008 l = 7.008 × 1000
= 7008 ml
7.0 0
8
9.0 3

To convert from a larger unit
to a smaller unit, you
multiply.

Let’s Try!
a) 10.03 m = ×
= cm
b) 4.125 kg = ×
= g
10.03 100
1003
4.125 1000
4125

Let’s Try!
c) 8.9 km = ×
= m
d) 3.76 l = ×
= ml
8.9 1000
8900
3.76 1000
3760

a) Express 12.43 m in metres and centimetres.
12.43 m = 12 m + 0.43 m
= 12 m 43 cm
b) Express 9.7 kg in kilograms and grams.
9.7 kg = 9 kg + 0.7 kg
= 9 kg 700 g
0.43 m = 0.43 × 100
= 43 cm
0.7 kg = 0.7 × 1000
= 700 g

c) Express 4.016 km in kilometres and metres.
4.016 km = 4 km + 0.016 km
= 4 km 16 m
d) Express 10.008 l in litres and millilitres.
10.008 l = 10 l + 0.008 l
= 10 l 8 ml
0.016 km = 0.016 × 1000
= 16 m
0.008 l = 0.008 × 1000
= 8 ml

Let’s Try!
a) 2.6 m = m + m
= m cm
b) 14.032 kg = kg + kg
= kg g
2 0.6
2 60
14 0.032
14 32

Let’s Try!
c) 20.47 km = km + km
= km m
d) 25.8 l = l + l
= l ml
20 0.47
20 470
25 0.8
25 800

a) Convert 208 cm to metres.
100 cm = 1 m
208 cm = 208 ÷ 100
= 2.08 m
b) Convert 3040 g to kilograms.
1000 g = 1 kg
3040 g = 3040 ÷ 1000
= 3.04 kg
2 0
8
3 0 4
0

c) Convert 5006 m to kilometres.
1000 m = 1 km
5006 m = 5006 ÷ 1000
= 5.006 km
d) Convert 10 900 ml to litres.
1000 ml = 1 l
10 900 ml = 10 900 ÷ 1000
= 10.9 l
1 0
9 0 0
5 0 0
6

To convert from a smaller
unit to a larger unit, you
divide.

Let’s Try!
a) 320 cm = ÷
= m
b) 4099 g = ÷
= kg
320 100
3.2
4099 1000
4.099

Let’s Try!
c) 9100 m = ÷
= km
d) 12 080 ml = ÷
= l
9100 1000
9.1
12 080 1000
12.08

a) Express 16 m 8 cm in metres.
16 m 8 cm = 16 m + 8 cm
= 16 m + 0.08 m
= 16.08 m
b) Express 7 kg 500 g in kilograms.
7 kg 500 g = 7 kg + 500 g
= 7 kg + 0.5 kg
= 7.5 kg
8 cm = 8 ÷ 100
= 0.08 m
500 g = 500 ÷ 1000
= 0.5 kg

c) Express 20 km 96 m in kilometres.
20 km 96 m = 20 km + 96 m
= 20 km + 0.096 km
= 20.096 km
d) Express 15 l 5 ml in litres.
15 l 5 ml = 15 l + 5 ml
= 15 l + 0.005 l
= 15.005 l
96 m = 96 ÷ 1000
= 0.096 km
5 ml = 5 ÷ 1000
= 0.005 l

Let’s Try!
a) 30 m 40 cm = m + m
= m
b) 8 kg 15 g = kg + kg
= kg
30 0.4
30.4
8 0.015
8.015

Let’s Try!
c) 16 km 109 m = km + km
= km
d) 30 l 300 ml = l + l
= l
16 0.109
16.109
30 0.3
30.3

A jug can hold three times as much water as a bottle.
3 jugs and 3 bottles can hold 10.2 l of water altogether.
Find the capacity of the bottle to the nearest litre.
Solving Word Problems
1 jug
1 bottle

3 jugs
3 bottles
10.2 l
?
12 units = 10.2 l

12 units = 10.2 l
1 unit = 10.2 ÷ 12
= 0.85 l
= 1 l (correct to the nearest l)
The capacity of the bottle correct to the nearest litre is 1 l.

Let’s Try!
A ruler is 6 times as long as a paperclip. The total length of
2 rulers and 2 paperclips is 35 cm. What is the length of
each paperclip in centimetres?
1 ruler
1 paperclip

Let’s Try!
A ruler is 6 times as long as a paperclip. The total length of
2 rulers and 2 paperclips is 35 cm. What is the length of
each paperclip in centimetres?
2 rulers
2 paperclips
35 cm
?
14 units = 35 cm
1 unit = 35 ÷ 14
= 2.5 cm
The length of each paperclip is 2.5 cm.

1 l of Grade A petrol costs $2.60 and 1 l of Grade B petrol
costs $2.05. A mechanic pays for 12 l of Grade A petrol and
22 l of Grade B petrol. How much does the mechanic pay
altogether?
Cost of 12 l of Grade A petrol = 12 × $2.60
= $31.20
Cost of 22 l of Grade B petrol = 22 × $2.05
= $45.10

1 l of Grade A petrol costs $2.60 and 1 l of Grade B petrol
costs $2.05. A mechanic pays for 12 l of Grade A petrol and
22 l of Grade B petrol. How much does the mechanic pay
altogether?
Total cost = $31.20 + $45.10
= $76.30
The mechanic pays $76.30 altogether.

Let’s Try!
1 m of blue ribbon cost $1.25 and 1 m of gold ribbon cost
$2.95. Linda bought 11 m of blue ribbon and 19 m of gold
ribbon. How much did Linda pay altogether?
11 m of blue ribbon = 11 × $1.25
= $13.75
19 m of gold ribbon = 19 × $2.95
= $56.05
Total cost = $13.75 + $56.05
= $69.80
Linda paid $69.80 altogether.

Learning Outcomes
Multiplying by 10, 100, 1000
and their multiples
5B
pp. 7 – 19
5B
pp. 3 – 13
Dividing by 10, 100, 1000
and their multiples
5B
pp. 20 – 33
5B
pp. 14 – 20
Converting measurements 5B
pp. 34 – 40
5B
pp. 21 – 27
Solving word problems 5B
pp. 41 – 45
5B
pp. 28 – 29
Reference — Textbooks

Primary 5 Mathematics Holistic Decimals.pptx

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