 Study P1 Mathematics Addition within 100 - Geniebook   1. Addition within 100 without renaming
2. Addition within 100 with renaming

## Topic Recap: Addition Within 20

Example 1:

How many chocolate tarts are there altogether? __________ + __________ = __________

14 tarts

Explanation:

You can add by counting on. $$11 + 3 = 14$$

There are 14 chocolate tarts altogether.

OR

Step 1:

$$11 = 10 + 1$$

Step 2:

Step 3:

\begin{align}​ 1 + 3 &= 4 \\ 10 + 4 &= 14 \\ 11 + 3 &= 14 \end{align}

There are 14 chocolate tarts altogether.

Example 2:

$$9 + 5 =$$ __________

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:

1. 17
2. 18
3. 19
4. 20

(2) 18

Explanation: Split 15 into 10 and 5.

$$15 + 3 = 18$$

## Topic Recap: Numbers Within 100

Example 1:

Complete the number pattern. $$10 + 86 = ?$$

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?

26 pencils

Explanation:

Step 1:

$$21 = 20 + 1$$

Step 2:

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.

26 pencils

Question 1:

1. 46
2. 47
3. 48
4. 49

Explanation:

Step 1:

$$45 = 40 + 5$$

Step 2:

Step 3:

\begin{align}​ 2 + 5 &= 7 \\ 40 + 7 &= 47 \\ 45 + 2 &= 47 \end{align}

(2) 47

OR $$45 + 2 = 47$$

(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:

Step 3:

\begin{align}​ 20 + 40 &= 60 \\ 60 + 1 &= 61 \\ 21 + 40 &= 61 \end{align}

They have 61 markers altogether.

61 markers

OR  They have 61 markers altogether.

61 markers

Question 1:

Explanation:

Step 1:

$$33 = 30 + 3$$

Step 2:

Step 3:

\begin{align}​ 30 + 50 &= 80 \\ 80 + 3 &= 83 \\ 33 + 50 &= 83 \end{align}

83

OR $$33 + 50 = 83$$

$$83$$

Example 3:

Jonathan has 44 crayons. May has 52 crayons. How many crayons do they have altogether?

Explanation:  They have 96 crayons altogether.

96 crayons

Question 1:

1. 35
2. 55
3. 57
4. 75

Explanation: $$31 + 24 = 55$$

(2) 55

Question 2:

The sum of 74 and 23 is __________.

1. 51
2. 57
3. 91
4. 97

Explanation:

Sum means  ‘$$+$$’. $$74 + 23 = 97$$

(4) 97

Question 3:

4 tens $$+$$ 2 tens $$=$$ __________

1. 6
2. 16
3. 60
4. 66

Explanation:

4 tens $$=$$ 40

2 tens $$=$$ 20 $$40 + 20 = 60$$

(3) 60

Question 4:

Which of the following is the sum of 3 tens and 68? Explanation:

3 tens $$=$$ 30

$$30 + 68 = 98$$

(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.

35 apples

Question 1:

Solve the following:

$$37 + 5 =$$ __________

1. 12
2. 32
3. 42
4. 52

Explanation: $$37 + 5 = 42$$

(3) 42

Question 2:

Solve the following:

$$45 + 19 =$$ __________

1. 64
2. 65
3. 66
4. 67

Explanation: $$45 + 19 = 64$$

(1) 64

Question 3:

The sum of 34 and 26 is __________.

1. 8
2. 50
3. 52
4. 60

Explanation: $$34 + 26 = 60$$

(4) 60

Question 4:

Add 7 ones to 5 tens 8 ones. The answer is __________.

1. 55
2. 58
3. 65
4. 83

Explanation:

7 ones $$=$$ 7

5 tens 8 ones $$=$$ 58 $$58 + 7 = 65$$

(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:

$$23 + 37 = 60$$

(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.

(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.

10 paper clips

Question 1:

The sum of 7, 8 and 9 is __________.

1. 23
2. 24
3. 25
4. 34

Explanation:

\begin{align}​ 7 + 8 &= 15 \\ 15 + 9 &= 24 \end{align}

(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}

(4) 7 tens 18 ones

## Challenge yourself!

Question 1:

Find the missing number in the box. 1. 16
2. 26
3. 36
4. 46

Explanation:

\begin{align}​ 24 + 12 &= 36 \\ ? + 10 &= 36 \\ 10 + 26 &= 36 \end{align}

(2) 26

• Addition within 100 without renaming
• Addition within 100 with renaming

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