Numeracy Strategies Worksheets Page 8
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3216
NUMERACY STRATEGIES
(Chapter 1)
‘Saving hundreds’
COMPUTER
We can solve the problem 176 + ¤ = 200 in stages.
DEMO
6 +
4
= 10 then 17 tens + 10 = 180 and 180
+
20
= 200
So, 24 has been added and 176 + 24 = 200.
EXERCISE 1A.13
1
Use play money to help you solve these problems:
a
b
c
383 + ¤ = 400
646 + ¤ = 800
¤ + 359 = 400
d
e
f
628 + ¤ = 800
117 + ¤ = 400
¤ + 86 = 300
g
h
472 + ¤ = 600
595 + ¤ = 800
2
Using the same method, do these mentally:
a
b
c
378 + ¤ = 900
456 + ¤ = 1000
9 + ¤ = 7000
d
e
f
¤ + 2340 = 6000
640 + ¤ = 5000
804 + ¤ = 2000
g
h
3992 + ¤ = 5000
704 + ¤ = 4000
COMPUTER
‘Jumping the number line’
DEMO
Jumping to and through tidy numbers is a fast way of doing some additions.
For example: To solve 26 + ¤ = 83 we can jump to 30, then to 80, then to 83.
So, 26
+
4
= 30, then 30
+
50
= 80, then 80
+
3
= 83.
PRINTABLE
We have added 57, so, 26 + 57 = 83.
WORKSHEET
+4
+50
+3
26 30
80 83
EXERCISE 1A.14
1
Use a number line to solve these:
a
b
c
d
14 + ¤ = 36
27 + ¤ = 51
36 + ¤ = 54
¤ + 27 = 48
e
f
g
h
¤ + 17 = 84
29 + ¤ = 75
8 + ¤ = 93
42 + ¤ = 76
2
Use the same method to do these mentally:
a
b
c
d
17 + ¤ = 42
32 + ¤ = 89
76 + ¤ = 93
¤ + 36 = 87
e
f
g
h
¤ + 14 = 75
¤ + 44 = 88
23 + ¤ = 74
45 + ¤ = 98
‘Problems like 23
+
¤
=
71’
This strategy is similar to Jumping the number line. We jump by a tidy number and then
jump back a small amount.
For example:
To solve 23 + ¤ = 71 we can jump by
50
to get to 73.
PRINTABLE
WORKSHEET
But we have gone too far by 2.
COMPUTER
So, we have moved
48
to the right on the number line
DEMO
which means that
23 + 48 = 71
.
Could we also do this by first going back 2 and then forward 50?
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