Numeracy Strategies Worksheets Page 15
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3223
NUMERACY STRATEGIES
(Chapter 1)
6
If it normally takes 589 days to sail around the world, and Snapdragon did it 48 days
faster than this, how long did it take for Snapdragon to complete the circuit?
‘Subtraction in parts’
Example: Richard has $48 and spends $23 of it. How much does he have left?
We start with $48 and split it into $40 + $5 + $3.
Taking away $20 and $3 results in $20 and $5 being left over.
COMPUTER
DEMO
So, $48 ¡ $23 = $25
You could use materials to model this subtraction.
EXERCISE 1B.5
1
If necessary, use materials to model and find these:
a
12 ¡ 5
b
16 ¡ 8
c
29 ¡ 5
d
39 ¡ 17
2
Without using materials, find these:
a
68 ¡ 25
b
85 ¡ 31
c
77 ¡ 46
d
87 ¡ 52
e
48 ¡ 34
f
84 ¡ 41
g
96 ¡ 43
h
69 ¡ 47
3
Make up some word problems where this strategy has to be used to solve them. The
answers they have are given below. Give the problems (but not the answers) to your
partner to solve.
a
32 minutes
b
76 kg
c
23 cm
d
45 km
e
$25
f
82 litres
g
57 degrees
h
42 sec
‘Comparisons’
As for addition, we are trying to find the difference between two amounts without counting
from one to the other.
For example, Jarrod travels 23 km to school on the bus and Sally travels 15 km.
How much further does Jarrod travel?
We can write 23 ¡ 15 = 8 or 15 + ¤ = 23.
So, Jarrod travels 8 km further.
EXERCISE 1B.6
1
If necessary, use materials to build and compare the numbers to find:
a
17 ¡ 8
b
23 ¡ 18
c
14 ¡ 8
d
27 ¡ 22
e
36 ¡ 27
f
45 ¡ 39
g
89 ¡ 78
h
92 ¡ 85
2
Find these without using materials:
a
34 ¡ 28
b
62 ¡ 57
c
81 ¡ 77
d
42 ¡ 38
e
66 ¡ 48
f
53 ¡ 42
g
96 ¡ 79
h
77 ¡ 59
3
Choose any three parts of question
2
and write a word problem for your partner to solve.
4
Try writing some word problems of your own for your partner or teacher to solve.
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