The document provides strategies for first-grade students to mentally add numbers, focusing on techniques like counting on and making an addend of 10. It includes examples and activities to illustrate these methods, demonstrating how to solve addition problems accurately. The goal is to enhance mental math skills and make addition easier for young learners.

1. Adding Numbers
Mentally
Grade 1

2. Visualize and add the following numbers
using appropriate techniques:
a. two one-digit numbers with sums up
to 18
b. three one-digits numbers
c. numbers with sums through 99
without and with regrouping

3. One Tuesday afternoon, Paolo was
doing his math homework. His
teacher gave him this addition
sentence.
8+6=____
He tried using his fingers to count.
However, he realized he does not
have enough fingers to add 8 and 6.

4. Here are some ways to help him find
the answer.
1. Count on.
Put the bigger number in your head.
Then, count 6 more from there.
Put 8 in your head. Then, count 6 more:
9,10,11,12,13,14
The last number in the counting is the
answer.
Thus, 8+6=14.

6. Another example:
7+5=_____
12
12+6=_____
18
27+4=_____
31

7. 2. Make an addend 10.
Using the bigger number 8, how many
more do you need to reach 10?
Get 2 from 6 to make 8 into 10.
How many are left after you take 2
from 6? You have 4 left.
Mentally do this:
8+6=(8+2)+(6-2)
=10+4
=14
Thus,
8+6=14.

8. Another activity for step 2.
35+5=_____ 35+5= 30+(5+5)
=30+10
=40
12+5=_____ 12+5=10+(2+5)
=10+7
=17

9. When adding mentally, here are
some techniques that can be
used.
1. Count on.
2. Make an addend 10.
Why is it important for you to
learn how to add numbers
mentally?

10. Using the count on technique to
find the sum. Write the missing
numbers on the space provided.
1. 9+5= ___in your head; count 5 more: __
2. 8+7= ___in your head; count 7 more: __
3. 7+6= ___in your head; count 6 more: __
4. 8+4= ___in your head; count 4 more: __

11. Formative!

12. Homework:

13. Thank you!