addingnumbersmentally-grade1-201114045705.pptx

The basic idea is to add in parts, such as tens and ones separately, or add in parts in some other way. Example 1. Add in parts 40 + 55. First break 55 into its tens and ones. 55 is 50 + 5.

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.

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

6. 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) Thus, 8+6=14. =10+4 =14

7. 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

8. 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?

9. 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: __