The document provides examples and practice problems for addition. It begins with examples of adding numbers by making tens and hundreds. Next, it shows how to break up or round numbers when adding. Then, it gives examples of expressing numbers as the sum of 2 or 3 other numbers. Several practice problems follow for students to work through. The problems involve adding multiple numbers together and expressing numbers as sums.

1. Lesson 3 ADDITION
Examples
(A) Making tens and hundreds
Example 1: Add the number by making tens.
(a) 3 + 5 + 7
= 10 + 5
= 15
(b) 4 + 7 + 6
= 10 + 7
= 17
(c) 5 + 4 + 5
= 10 + 4
= 14
(d) 2 + 9 + 8
= 10 + 9
=19
(e) 4 + 5 + 6 + 5
= 10 + 10
= 20
(f) 7 + 8 + 2 + 3
= 10 + 10
= 20
Example 2: Add the numbers by making tens or hundreds.
(a) 35 + 15 + 65
=100 + 15
=115
(b) 45 + 55 + 20
= 100 + 20
= 120
(c) 38 + 22 + 16
= 60 + 16
= 76
(d) 42 + 16 + 38
= 80 + 16
= 96
(e) 15 + 32 + 48 + 5
= 80 + 20
= 100

2. (f) 17 + 13 + 25 + 35
= 30 + 60
= 90
(B) Breaking up or Rounding up numbers
Example 1: Find the value of 17 + 18 + 19.
17 + 18 + 19 = 20 – 3 + 20 – 2 + 20 – 1
= 60 – 3 – 2 – 1
=60 – 6
= 54
Example 2: Find the value of 37 + 38 + 35.
37 + 38 + 35 = 30 + 7 + 30 + 8 + 30 + 5
= 90 + 7 + 8 + 5
= 90 + 7 + 8 + 3 + 2
=90 + 20
= 110
Example 3: Find the value of 17 + 21 + 14.
17 + 21 + 14 = 17 + 3 + 11 + 21
= 20 + 32
= 52
Example 4: Find the value of 9 + 99 + 999.
9 + 99 + 999 = 10 – 1 + 100 – 1 + 1000 – 1
= 1000 + 100 + 10 – 3
= 1107

3. (C) Express a number as a sum of 2 or 3 numbers
Example 1: 2 3 5 7 11
13 17 19 23 29
Express each number below as the sum of 2 numbers given above.
(a) 10 = 7 + 3
(b) 12 = 7 + 5
(c) 18 = 5 + 13
Or
18 = 7 + 11
(d) 30 = 11 + 19
Or
30 = 13 + 17
Or
30 = 23 + 7
Example 2: 2 3 5 7 11 13
17 19 23 29 31 33
Express each number below as the sum of 3 numbers given above.
(a) 10 = 2 + 3 + 5
(b) 24 = 2 + 3 + 19
Or
24 = 2 + 5 + 17
(c) 46 = 2 + 13 + 31
Or
46 = 2 + 11 + 133
(d) 39 = 3 + 7 + 29
Or
39 = 3 + 17 + 19
a. 2 + 8 + 7
b. 5 + 4 + 6 + 5
c. 9 + 2 + 8 + 1

4. d. 14 + 16 + 21 + 29
e. 13 + 28 + 22 + 17
f. 15 + 37 + 23 + 25
g. 26 + 14 + 33 + 37
h. 18 + 19 + 22 + 11
i. 28 + 32 +15 + 25
j. 32 + 22 + 28 + 10
k. 42 + 16 + 15 + 18
l. 18 + 13 + 22 + 28
1. Find the values of the following
a. 9 + 8 + 10
b. 7 + 8 + 9
c. 7 + 8 + 11
d. 10 + 19 + 17
e. 18 + 19 + 20
f. 9 + 19 + 39
g. 18 + 28 + 38
h. 16 + 17 + 18 + 19
2. Find the values of the following.
a. 18 + 19 + 13
b. 17 + 18 + 15
c. 21 + 22 + 23 + 24
d. 19 + 17 + 14 + 21
e. 33 + 24 + 13 + 14
f. 29 + 23 + 9 + 22
g. 29 + 23 + 28 + 16
h. 27 + 4 + 29 + 35
3. 2 3 5 7 11
13 17 19 23 29
Express each number below as the sum of 2 numbers given above.
a. 7 = ( ) +( )
b. 12 = ( ) + ( )
c. 18 = ( ) + ( )
d. 36 = ( ) + ( )
36 = ( ) + ( )
36 = ( ) + ( )
e. 42 = ( ) + ( )
42 = ( ) + ( )
f. 48 = ( ) + ( )
4. Express each number as the sum of 3 numbers given in question 4.

5. a. 10 = ( ) + ( ) + ( )
b. 23 = ( ) + ( ) + ( ) + ( ) + ( ) + ( )
c. 38 = ( ) + ( ) + ( ) + ( ) + ( ) + ( )
d. 37 = ( ) + ( ) + ( ) + ( ) + ( ) + ( )
e. 41 = ( ) + ( ) + ( ) + ( ) + ( ) + ( )
f. 49 = ( ) + ( ) + ( ) + ( ) + ( ) + ( )
5. Fill in each box with the correct answer to make the addition works.
a. 3
+ 3
Solve by Comparison and Replacement
Practice
3. + = 14
- = 6
= ? = ?
4. + = 15
- = 7
= ? = ?
5. - = 22
+ = 30
= ? = ?
6. + + = 15
+ = 11
= ? = ?

6. Chapter 3
1. (a) 2 + 8 + 3 + 7 = 10 + 10
= 20
(b) 5 + 4 + 6 + 5 = 10 + 10
= 20
(c) 9 + 2 + 8 + 1 = 10 + 10
=20
(d) 14 + 16 + 21 + 29 = 30 + 30
= 80
(e) 13 + 28 + 22 + 17 = 30 + 50
= 80
(f) 15 + 37 + 23 + 25 = 60 + 40
= 100
(g) 26 + 14 + 33 + 37 = 40 + 70
= 110
(h) 18 + 19 + 22 + 11 = 40 + 30
= 70
(i) 28 + 32 + 15 + 25 = 60 + 40
= 100
(j) 32 + 22 + 28 + 10 = 32 + 50 + 10
= 92
(k) 42 + 16 + 15 + 18 = 60 + 16 + 4 + 11
= 80 + 11
= 91
(l) 18 + 13 + 22 + 28 = 18 + 2 + 11 + 50
= 20 + 11 + 50
= 81

7. 2. (a) 9 + 8 + 10 = 10 – 1 + 10 – 2 + 10
= 30 – 3
= 27
(b) 7 + 8 + 9
= 10 – 3 + 10 – 2 + 10 – 1
= 30 – 6
= 24
(c) 7 + 8 + 9 + 11 = 7 + 3 + 5 + 20
= 10 + 5 + 20
= 35
(d) 10 + 19 + 17
= 10 + 20 – 1 + 20 – 3
= 50 – 4
= 46
(e) 18 + 19 + 20
= 20 – 2 + 20 – 1 + 20
= 60 – 3
= 57
(f) 9 + 19 + 39
= 10 – 1 + 20 – 1 + 40 – 1
= 70 – 3
= 67
(g) 18 + 29 + 20
= 20 – 2 + 30 – 2 + 40 – 2
= 90 – 6
= 84

8. (h) 16 + 17 + 18 + 19
= 10 + 3 + 2 + 1 + 17 + 18 + 19
= 10 + 20 + 20 + 20
= 70
3. (a) 18 + 19 + 13 = 18 + 19 + 2 + 1 + 10
= 20 + 20 + 10
= 50
(b) 17 + 18 + 15 = 17 + 18 + 3 + 2 + 10
= 20 + 20 + 10
= 50
(c) 21 + 22 + 23 + 24
= 20 + 1 + 20 + 2 + 20 + 3 + 20 + 4
= 20 × 4 + 1 + 2 + 3 + 4
= 80 + 10
= 90
(d) 19 + 17 + 13 + 14 + 21
= 19 + 21 + 17 + 3 + 11
= 40 + 20 + 11
= 71
(e) 33 + 24 + 13 + 14
= 30 + 3 + 20 + 4 + 10 + 3 + 14
= 60 + 10 + 14
= 84
(f) 28 + 23 + 9 + 22 = 50 + 22 + 1 + 9
= 50 + 22 + 10
= 82

9. (g) 29 + 23 + 28 + 16
= 29 + 1 + 20 + 2 + 28 +_16
= 30 + 30 + 36
= 96
(h) 27 + 4 + 29 + 35 = 27 + 3 + 1 + 29 + 35
= 30 + 30 + 35
= 95
4 (a) 7 = 2 + 5
(b) 12 = 5 + 7
(c) 18 = 5 + 13
18 = 7 + 11
(d) 36 = 13 + 23
36 = 17 + 19
36 = 29 + 7
(e) 42 = 19 + 23
42 = 29 + 13
(f) 48 = 19 + 29
5 (a) 10 = 2 + 3 + 5
(b) 23 = 3 + 7 + 13 = 5 + 7 + 11
(c) 38 = 2 + 7 + 29 = 2 + 13 + 23
(d) 37 = 3 + 5 + 29 = 3 + 11 + 23 or = 13 + 17 + 7
(e) 41 = 5 + 17 + 19 = 5 + 13 + 23 or = 5 + 7 + 29 = 7 + 11 + 23
(f) 49 = 3 + 17 + 29 = 7 + 13 + 29 or = 7 + 13 + 29 or = 7 + 19 + 23 = 13 + 17 + 19