## Key Concepts

- Add numbers using place value.
- Use properties of operation to find the sum.
- Solve few model questions related to addition by using place

### Place Value Blocks

**Question 1: **

Represent the number 58 using place value blocks.

**Answer: **

58 is written as 5 tens and 8 ones.

**Question 2: **

Elena picked 38 flowers from the garden. Mary picked 25 flowers from the same garden. How many flowers did they pick in all? Use place-value blocks to find the sum.

**Answer: **

Flowers picked by Elena = 38

Flowers picked by Mary = 25

Total flowers picked by Elena and Mary is the sum of 38 and 25.

Let’s use place-value blocks to find the sum of 38 and 25.

38 is written as 3 tens and 8 ones.

25 is written as 2 tens and 5 ones.

The sum of 38 and 25 = 38 + 25

Join the tens and ones of 38 and 25

Regrouping 13 ones as 1 ten & 3 ones

38 + 25 = 63

So, the total number of flowers picked by Elena and Mary is 63.

### Representation of 2-digit numbers using place value blocks (dots and lines)

#### Place Value Block

We can represent the addend using quick drawing as lines and dots.

Representation of a single dot as 1 one.

Representation of single line as 1 ten.

Remember:

10 ones combine to make 1 ten.

**Example 1: **

Represent the number 48 using the place value block.

**Answer: **

48 is written as 4 tens and 8 ones.

**Example 2: **

Represent the number 72 using the place value block.

**Answer: **

72 is written as 7 tens and 2 ones.

### Sum of the 2-digit numbers using the place value blocks (dots and lines)

**Example 1: **

Find the sum of 34 and 55.

**Solution: **

**One way: **

34 is written as 3 tens and 4 ones.

55 is written as 5 ones and 5 tens.

The sum of 34 and 55 is given as below:

34 + 55 = 89

So, the sum of 34 and 55 is 89.

**Another way: **

To find the sum of 34 and 55.

34 is written as 3 tens 4 ones.

55 is written as 5 tens 5 ones.

The sum of 34 and 55 is:

8 tens and 9 ones is 89.

So, the sum of 34 and 55 is 89.

**Example 2: **

Find the sum of 43 and 19.

**Solution: **

**One way: **

Use quick drawing for addends.

And then join tens and ones.

Regroup 12 ones as 1 ten & 2 ones.

**Another way: **

To find the sum of 43 and 19.

43 is written as 4 tens 3 ones.

19 is written as 1 ten 9 ones.

The sum of 43 and 19 is:

12 ones is 1 ten 2 ones

5 tens 1 ten 2 ones

50 + 10 + 2 = 62

So, the sum of 43 and 19 is 62.

### Model question related to the sum of 2-digit numbers using place value block (dots and lines)

**Example: **

Kim counts 45 buttons. Then he counts 27 more buttons. How many buttons does Kim count in all?

**Answer: **

Number of buttons Kim counted in the first = 45

The number of buttons Kim counted the next time = 27

Total number of buttons Kim counted in all = Sum of 45 and 27

**One way: **

Let’s find the sum of 45 and 27 by drawing blocks for addends.

And then join tens and ones.

Regroup 12 ones as 1 ten and 2 ones.

45 + 27 = 72

So, Kim counted 72 buttons in all.

**Another way: **

To find the sum of 45 and 27.

45 is written as 4 tens 5 ones.

27 is written as 2 ten 7 ones.

The sum of 45 and 27 is:

12 ones is 1 ten 2 ones

6 tens 1 ten 2 ones

60 + 10 + 2 = 72

So, Kim counted 72 buttons in all.

#### Activity

Circle all the number pair in the box that match that sum.

## Exercise

**Question 1:**

Find the sum of 27 and 43. Draw place-value blocks to explain your work.

**Question 2:**

Find the sum of 52 and 39. Draw place-value blocks to explain your work.

**Question 3:**

In a class there are 30 desks and 46 chairs. How many desks and chairs are there in total?

**Question 4:**

Sasha plants 24 trees. Monica plants 38 trees. How many trees do they plant in all?

### Concept Map

### What we have learned

- Add numbers using place value blocks.
- Add numbers using properties of operation.
- Solve model question using place value blocks.

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