Transcript Numberline - Primary Resources

Using number lines
in Addition and
Subtraction
By Amani El-Alawneh
Adding numbers using
the number line.
25
47
So how do we do this using
the number line?
We use the strategy called:
Counting Up
You need to think about:
What number shall I start with on my
number line?
What number do we want to count up by?
Are there any number bonds that can help
me?
25 + 47 =
Use the counting up method!!
+20
+3
47
67
+2
70 72
So we start at the biggest number…47
And count up 25 places
What number do we end on???
So….
25 + 47 =
72
?
+ 34 = 57
Use the Counting
Strategy
Up
Remember -You need to think about:
What number shall I start with on my
number line?
What number do we want to count up by?
Are there any number bonds that can help
me?
+ 34 = 57
+10
+10
34
+3
44
54
34
So what is
10 + 10 + 3 = 23
So…..
23
+
34 = 57
57
57
Can I use the counting up
strategy for Subtraction too?
YES
Have a look at this question!
43 – 27 =
16
What number shall I start from on my number line?
What number do I want to get to?
What number shall count on by?
Can any number bond make counting on easier for me?
+10
27
10 + 3 + 3 = 16
+3
37
+3
40
43
32 -
= 18
What number shall I start from on my number line?
What number do I want to get to?
What number shall count on by?
Can any number bond make counting on easier for me?
+10
+2
+2
18
20
30
2 + 10 + 2 = 14
So….
32 -
14
= 18
32
Have a go at these questions now using number lines
and the counting on strategy:
1.
2.
3.
4.
5.
45 – 25 =
54 – 26 =
– 19 =36
28 –
= 14
43 – 37 =
6.
55 + 18 =
7.
29 + 40 =
8.
33 +
9.
= 51
+ 14 = 35
10. 22 + 15 =
Extra for Experts:
1. 154 – 147
6.
123 + 19
2. 172 – 133
7.
199 + 98
3. 198 – 188
8.
147 + 76
4. 134 – 119
9.
201 + 97
5. 176 - 134
10. 185 + 89
Work out the following
calculations mentally:
•
•
•
•
43 – 37
102 – 98
154 – 147
3005 – 2997
How can we show this using the
number line:
43 – 37
+3
+3
37
3+3=6
So,
40
43 – 37 = 6
43
154 – 147
+4
+3
3+4=7
So,
147
150
154
154 – 147 = 7
Have a look at these Calculations
• 144 – 138
• 89 – 34
What is it about the numbers that
made you decide to use mental
method or a number line?
• 134 – 123
• 125 - 76
Do you always need to use a number
line when the numbers are a
long way apart??
- 285 = 39
+
+
285
300