Addition Within 100
In this article, we will learn about Addition within 100. The learning objectives are:
- Addition within 100 without renaming
- Addition within 100 with renaming
- Addition of three numbers
Topic Recap: Addition Within 20
Example 1:
How many chocolate tarts are there altogether?
__________ + __________ = __________
Answer:
14 tarts
Explanation:
You can add by counting on.
\(11 + 3 = 14\)
There are 14 chocolate tarts altogether.
OR
You can also add by adding the ones first.
Step 1:
\(11 = 10 + 1\)
Step 2:
Add the ones first.
Step 3:
\(\begin{align} 1 + 3 &= 4 \\ 10 + 4 &= 14 \\ 11 + 3 &= 14 \end{align}\)
There are 14 chocolate tarts altogether.
Example 2:
\(9 + 5 =\) __________
Answer:
14
Explanation:
You can also add by making 10 first.
Step 1:
\(9 = 4 + 5\)
Step 2:
Make 10 first.
Step 3:
\(\begin{align} 5 + 5 &= 10 \\ 10 + 4 &= 14\\ 9 + 5 &= 14 \end{align}\)
Example 3:
Add 15 and 3.
- 17
- 18
- 19
- 20
Answer:
(2) 18
Explanation:
Split 15 into 10 and 5.
Add 5 to 3.
Add the total to 10.
\(15 + 3 = 18\)
Topic Recap: Numbers Within 100
Example 1:
Complete the number pattern.
\(10 + 86 = ?\)
Answer:
96
Explanation:
10 more than 86 is 96.
\(10 + 86 = 96\)
1. Addition Within 100 Without Renaming
Example 1:
Damien has 21 pencils. Claire has 5 pencils. How many pencils do they have altogether?
Answer:
26 pencils
Explanation:
Step 1:
\(21 = 20 + 1\)
Step 2:
Add the ones first.
Step 3:
\(\begin{align} 1 + 5 &= 6 \\ 20 + 6 &= 26 \\ 21 + 5 &= 26 \end{align}\)
They have 26 pencils altogether.
So the answer is 26 pencils
OR
They have 26 pencils altogether.
Answer:
26 pencils
Question 1:
Add 45 to 2.
- 46
- 47
- 48
- 49
Explanation:
Step 1:
\(45 = 40 + 5\)
Step 2:
Add the ones first.
Step 3:
\(\begin{align} 2 + 5 &= 7 \\ 40 + 7 &= 47 \\ 45 + 2 &= 47 \end{align}\)
Answer:
(2) 47
OR
\(45 + 2 = 47\)
Answer:
(2) 47
Example 2:
Jocelyn has 21 markers and Donnie has 40 markers. How many markers do they have altogether?
Explanation:
Step 1:
\(21 = 20 + 1\)
Step 2:
Add the tens first.
Step 3:
\(\begin{align} 20 + 40 &= 60 \\ 60 + 1 &= 61 \\ 21 + 40 &= 61 \end{align}\)
They have 61 markers altogether.
Answer:
61 markers
OR
They have 61 markers altogether.
Answer:
61 markers
Question 1:
Add 33 to 50.
Explanation:
Step 1:
\(33 = 30 + 3\)
Step 2:
Add the tens first.
Step 3:
\(\begin{align} 30 + 50 &= 80 \\ 80 + 3 &= 83 \\ 33 + 50 &= 83 \end{align}\)
Answer:
83
OR
\(33 + 50 = 83\)
Answer:
\(83\)
Example 3:
Jonathan has 44 crayons. May has 52 crayons. How many crayons do they have altogether?
Explanation:
They have 96 crayons altogether.
Answer:
96 crayons
Question 1:
Add 31 and 24.
- 35
- 55
- 57
- 75
Explanation:
\(31 + 24 = 55\)
Answer:
(2) 55
Question 2:
The sum of 74 and 23 is __________.
- 51
- 57
- 91
- 97
Explanation:
Sum means ‘\(+\)’.
\(74 + 23 = 97\)
Answer:
(4) 97
Question 3:
4 tens \(+\) 2 tens \(=\) __________
- 6
- 16
- 60
- 66
Explanation:
4 tens \(=\) 40
2 tens \(=\) 20
\(40 + 20 = 60\)
Answer:
(3) 60
Question 4:
Which of the following is the sum of 3 tens and 68?
Explanation:
3 tens \(=\) 30
\(30 + 68 = 98\)
Answer:
(3) 98
2. Addition Within 100 With Renaming
Example:
26 apples were sold in the morning. 9 apples were sold in the afternoon. How many apples were sold altogether?
Explanation:
\(26 + 9 = 35\)
35 apples were sold altogether.
Answer:
35 apples
Question 1:
Solve the following:
\(37 + 5 =\) __________
- 12
- 32
- 42
- 52
Explanation:
\(37 + 5 = 42\)
Answer:
(3) 42
Question 2:
Solve the following:
\(45 + 19 =\) __________
- 64
- 65
- 66
- 67
Explanation:
\(45 + 19 = 64\)
Answer:
(1) 64
Question 3:
The sum of 34 and 26 is __________.
- 8
- 50
- 52
- 60
Explanation:
\(34 + 26 = 60\)
Answer:
(4) 60
Question 4:
Add 7 ones to 5 tens 8 ones. The answer is __________.
- 55
- 58
- 65
- 83
Explanation:
7 ones \(=\) 7
5 tens 8 ones \(=\) 58
\(58 + 7 = 65\)
Answer:
(3) 65
Question 5:
Which of the following has the greatest answer?
Explanation:
Option 1:
\(28 + 19 = 47\)
Option 2:
\(36 + 12 = 48\)
Option 3:
\(38 + 16 = 54\)
Option 4:
\(23 + 37 = 60\)
The greatest answer is 60.
Answer:
(4) 60
Question 6:
Which of the following numbers comes just after the sum of 29 and 55?
Explanation:
\(29 + 55 = 84\)
The number that comes just after 84 is 85.
Answer:
(3) 85
3. Addition Of Three Numbers
Example:
Elizabeth has 1 paper clip. Jackie has 4 paper clips and Joey has 5 paper clips. How many paper clips do the children have in all?
Explanation:
\(\begin{align} 1 + 4 &= 5 \\ 5 + 5 &= 10 \end{align}\)
The children have 10 paper clips in all.
Answer:
10 paper clips
Question 1:
The sum of 7, 8 and 9 is __________.
- 23
- 24
- 25
- 34
Explanation:
\(\begin{align} 7 + 8 &= 15 \\ 15 + 9 &= 24 \end{align}\)
Answer:
(2) 24
Question 2:
Which of the four options does not have the same value as the sum of 33 and 45?
Explanation:
\(33 + 45 = 78\)
We have to find an option that is not equal to 78.
Option 1:
78
Option 2:
\(\begin{align} 50 + 10 + 18 \\\\ 50 + 10 = 60 \\ 60 + 18 = 78 \end{align}\)
Option 3:
6 tens and 18 ones
6 tens \(=\) 60
18 ones \(=\) 18
6 tens and 18 ones
\(\begin{align} &= 60 + 18\\ &= 78 \end{align}\)
Option 4:
7 tens and 18 ones
7 tens \(=\) 70
18 ones \(=\) 18
7 tens and 18 ones
\(\begin{align} &= 70 + 18 \\ &= 80 \end{align}\)
Answer:
(4) 7 tens 18 ones
Challenge yourself!
Question 1:
Find the missing number in the box.
- 16
- 26
- 36
- 46
Explanation:
\(\begin{align} 24 + 12 &= 36 \\ ? + 10 &= 36 \\ 10 + 26 &= 36 \end{align}\)
Answer:
(2) 26
In this article, we have learnt:
- Addition within 100 without renaming
- Addition within 100 with renaming
- Addition of three numbers
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