Add 2 Digit Number Using Models

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.