Adding in our heads
We are learning to add two 2-digit numbers together in our
heads.
Adding on a multiple of ten
Let’s count in ten’s starting
from the number 3
When we count on in tens,
our finger jumps down the
hundred square.
We’re going to solve this
sum …
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33 +10 =
Find number 33 on the hundred square
then jump down once.
What number
This do
is our
youanswer.
land on?
43
Let’s solve some more
sums.
53 +20=
Find the number 53 on the
23+40
= This time
hundred
square.
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100
we
are
adding
20,23
that’s
Find
the
number
on the
two
jumpssquare.
of ten, This
so we
hundred
time
need
to adding
jump down
twice.
we are
40, that’s
four jumps of ten, so we
need to jump down four
What number do we land on?
times.
What number do we land on?
73
63
Now try these ...
27 + 30 = 57
19 + 50 = 69
36 + 20 = 56
Find this
number
Find this
number
Find this
number
Three jumps
of ten.
Five jumps of
ten.
Two jumps of
ten.
Now have a go at
some of your own …
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1) 23 + 10 = 33
11) 29 + 50 = 79
21) 18 + 30 = 48
2) 37 + 20 = 57
12) 61+ 20 =81
22) 55 + 40 = 95
3) 25 + 40 = 65
13) 22 + 40 = 62
23) 24 + 50 = 74
4) 31 + 10 = 41
14) 74 + 10 = 84
24) 37 + 20 = 57
5) 45 + 40 = 85
15) 43 + 40 = 83
25) 62 + 30 = 92
6) 24 + 30 = 54
16) 56 + 20 = 76
26) 78 + 30 = 108
7) 42 + 20 = 62
17) 49 + 30 = 79
27) 45 + 70 = 115
8) 57 + 40 = 97
18) 17+ 50 =67
28) 61 + 60 = 121
9) 76 + 10 = 86
19) 22 + 40 = 62
29) 92 + 20 = 112
10) 38 + 40 =78
20) 13 + 60 = 73
30) 86 + 20 = 106
Now we are ready for the tricky ones!
24 + 24
10
5+
=15 39
34
•We are going to start with the number 24.
•We need to split up (partition) the number 15
to make it easier to solve.
•Now 24 + 10 = 34
And 34 + 5 = 39
•This means the answer to 24 + 15 = 39
31 + 10
31
6+
=16 47
41
•We are going to start with the number 31.
•We need to split up (partition) the number 16
to make it easier to solve.
•Now 31 + 10 = 41
And 41 + 6 = 47
•This means the answer to 31 + 16 = 47
Now you are ready to try
some on your own …