Subtraction by
counting on
Key Words
Subtraction = taking away
Lesson Aim: To
know how to
subtract numbers
to 100 by counting
on
How do you solve 99-45 by
counting on?
• 45
• 99 ?
We count on.
Here is how…..
Think !
We added 5+40+9= 54
99-45=54
45+5=50
50+40=90
90+9=99
add 5
45
add 40
50
add 9
90
99
Counting on always:
starts with the number being
taken away
ends with the number that has
something taken away from it
WE find the DIFFERENCE between the two numbers.
If you need more help
please ask now…..
Solve these by counting on
78-89=
94-56=
67-53=
88-32=