Add More than Two 2-Digit Numbers

Key Concepts

• Addition of three or more 2-digit numbers.
• Add 2-digit numbers using different strategies.

Addition of more than two 2-digit numbers   

We can add more than two 2-digit numbers in different ways as given below:  

One way:  

1. For each addend, draw tens and ones.  

2. Join the tens and join the ones.  

3. Then add the partial sums. 

Another way:  

1. Use the commutative property to make a ten.  

2. Then, find the sum.  

Add more than two 2-digit numbers:    

Example 1:  

Find 33 + 28 + 17.  

Answer:  

One way:  

For each addend draw tens and ones. 

Now join the tens and join the ones.  

Write the partial sums and find the sum. 

So, 33 + 28 + 17 = 78 

Another way:  

33 + 28 + 17    

Let’s use the commutative property.    

50 + 28 = 78 

So, 33 + 28 + 17 = 78.  

Example 2 :  

Find 21 + 27 + 19 + 15.  

Answer:  

One way:  

For each addend, draw tens and ones. 

Now join the tens and join the ones.  

Write the partial sums and find the sum. 

So, 21 + 27 + 19 + 15 = 82.  

Another way:     

21 + 27 + 19 + 15    

Let’s use the commutative property.    

40 + 42 = 82 

So, 21 + 27 + 19 + 15 = 82. 

Model question

Question:  

A strawberry farm opened to the public last week. There were 18 strawberry plants in the first row and 21 plants in the second row. The farmer made the third row and planted 12 more strawberry plants. How many strawberry plants were there in the 3 rows? 

Answer:  

Number of plants in the first row = 18 

Number of plants in the second row = 21 

Number of plants in the third row = 12 

To find the total number of strawberry plants in the 3 rows, we must find the sum of 18, 21, and 12.  

18 + 21 + 12 = ? 

One way:  

For each addend, draw tens and ones. 

Now join the tens and join the ones.  

Write the partial sums and find the sum. 

18 + 21 + 12 = 51  

So, there are 51 strawberry plants in the 3 rows.  

Another way:     

18 + 21 + 12    

Let’s use the commutative property.    

30 + 21 = 51  

18 + 21 + 12 = 51  

So, there are 51 strawberry plants in the 3 rows.

Exercise

Question 1:

Find the sum of 43, 16, and 27.

Question 2:

Find 15 + 27 + 14 + 25.

Question 3:

Fill in the blank: 40 + ___ + 5 = 49.

Question 4:

Fill in the blank: 12 + 15 + 18 = ___.

Question 5:

The farmer made fruit jam for extra income. He sold 28 bottles of jam at the farm, and he delivered another 13 bottles of jam to another place. There were 12 bottles of jam left on the display. How many of the bottles of fruit jam did he make altogether?

Question 6:

Isabella’s hair is 18 inches long. If her hair grows 4 more inches each month, how long will it be in two more months?

Question 7:

Write the addition equation for this sentence: “Jenny bought 2 skirts for $8 each and a pair of shorts for $11. So, she spent $27 on clothing altogether.”

Question 8: Richard fills the catering cart with 37 cans of soda, 25 cans of fresh juice and 15 cans of coke.

Question 9:

Write the addition sentence that fits this: “There are 3 flight attendants serving the first class and business class and 6 flight attendants serving the economy class. There are 9 flight attendants working on the flight.”

Question 10: At the soda dispenser, there are 31 large paper cups, 23 medium

Concept Map

What we have learned

• Add three or more 2-digit numbers.
• Solve the questions by using strategies based on the place value and properties of operations.