Numeracy Strategies Worksheets Page 16
ADVERTISEMENT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
3224
NUMERACY STRATEGIES
(Chapter 1)
‘Don’t subtract, add’
Sometimes when we have a subtraction to do it is easier to do addition. We can use jumping
the number line strategy to find the answer.
For example, Tayla’s bag of candy has 48 pieces in it while Georgia’s has 63.
Who has the most candy?
We can solve the problem by subtraction, using 63 ¡ 48
or we can use addition, 48 + ¤ = 63.
EXERCISE 1B.7
1
Use addition and jumping the number line to find:
a
73 ¡ 16
b
81 ¡ 75
c
37 ¡ 16
d
74 ¡ 58
2
Using the same strategy, but without using materials, find:
a
93 ¡ 87
b
28 ¡ 17
c
56 ¡ 39
d
87 ¡ 34
e
63 ¡ 33
f
75 ¡ 39
g
102 ¡ 85
h
122 ¡ 104
‘When one number is near a hundred’
In this strategy we adjust a number which is near one hundred to 100, before subtracting.
For example, Allesha withdraws $44 from her bank account which had $97 in it.
How much money is left in the account?
We can add $3 to the $97 to make it $100 and then subtract the $44.
$100 ¡ $44 = $56, but we must subtract the $3 which we added to make
up the $100.
So, she has in her account $97 + $3 ¡ $44 ¡ $3 = $100 ¡ $47 = $53.
EXERCISE 1B.8
1
If necessary, use money to help you find these with the strategy shown above:
a
$98 ¡ $34
b
$88 ¡ $23
c
$103 ¡ $42
d
$92 ¡ $67
2
Using the same strategy, do these mentally:
a
$96 ¡ $78
b
$89 ¡ $65
c
$91 ¡ $77
d
$105 ¡ $65
3
Find these harder subtractions: (Think carefully about which number to adjust.)
a
167 ¡ 103
b
207 ¡ 64
c
368 ¡ 197
d
1065 ¡ 99
‘Problems like 73
¡
19
= ¤
’
Another very good strategy to use is to subtract a tidy number and then adjust the answer.
We can best show this using number lines.
For example, Jason was to take 64 people to the rugby, but 18 were
PRINTABLE
unable to come. How many does he take?
NUMBER LINES
We would think 64 ¡ 18
and to do this we subtract
+2
-20
20 from 64 and then
added back the extra 2.
40
45
50
55
60
65
70
So, 64 ¡ 18 = 64 ¡ 20 + 2 = 44 + 2 = 46:
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education