Unit 6 I have fifty markers Lesson 21 课件 25张PPT 无音视频

5+10=15
5x3=15
15=5+5+5
Let's write down the formula(算式)
Lesson twenty-one

Unit 6 I have fifty markers



Welcome to Lala's Maths class.
20
30
80
50
10
90
60
100
1.Do you know these numbers?

40
70
20
30
80
50
10
90
60
70
100
Let's read them.

40
What's missing?

10, ,30
10,20,30
What's missing?

30,40,50, ,
30,40,50,60,
What's missing?

50,60, , ,90
50,60,70,80,90
What's missing?

60,70,80, , ,
60,70,80,90,100
2.Do you know these marks?

plus
minus
Talk about them in your groups.

50,60,_____,______,90
What are the missing numbers?
Look at the numbers on the blackboard :
50 ,60, ___, ___, 90
Who can guess the missing numbers ?
So the missing numbers are seventy and eighty .
It’s easy . Fifty plus ten is sixty.
100,90,_____,______,60
So the missing numbers are eighty and seventy.
One hundred minus ten is ninety .
Ninety minus ten is eighty.
100-10=90
90-10=80
80-10=70
70-10=60
One hundred minus ten is ninety.
“—”

So the missing numbers are
eighty and seventy.
Well done !
fifty minus ten is forty.
forty plus twenty is sixty.


Eighty minus twenty is sixty.


One hundred minus thirty
is seventy.


Seventy plus ten is eighty.
One hundred minus ten is ninety.
Can you do it?
Fifty plus ten is ______.
One hundred minus twenty is _____.
Forty plus twenty is _______.
Ninety minus ten is ____







irty
rty
fty
xty
venty
ghty
nety
enty
guess the numbers
tw
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fo
fi
si
se
ei
ni
hun
dred