Add With Partial Sum

Key Concepts

• Addition of numbers using place value blocks.
• Addition of numbers using partial sums.
• Solve model questions related to addition by using partial

Partial Sums

With the help of place-value blocks, we can add and record a partial sum.  

Steps to follow for adding 2-digit numbers using partial sums:  

• Starting from the left, add up the numbers in the tens place.  
• Add up the numbers in ones place.  
• Add up all the partial sums.  

Example:  

Find 26 + 47.  

Solution:  

60 and 13 are partial sums. 

Step 3: Then add the partial sums to find the sums.  

So, 26 + 47 = 73.  

Question 1:  

Find the sum of 55 and 26 using partial sums.  

Answer:  

So, 55 + 26 = 81. 

Question 2:  

Find the sum of 34 and 23 using partial sums.  

Answer:  

So, 34 + 23 = 57. 

Question 3:  

Find the sum of 58 and 9 using partial sums.  

Answer:  

So, 58 + 9 = 67. 

Model question related to the sum of 2-digit numbers using partial sums

Question:  

Isabella read 23 books in the previous year. This year, she has read 32 books. Using partial sum, find the total number of books she has read across the two years.  

Answer:  

Number of books Isabella read in the previous year = 23 

Number of books Isabella read this year = 32   

The total number of books Isabella has read across the two years = 23 + 32  

The sum of 23 and 32 using partial sums:  

23 + 32 = 55.  

So, 55 books Isabella has read across the two years.  

Activity 

Exercise

Question 1:

Find the sum of 37 and 44 by using partial sums.

Question 2:

Use partial sums to find the sum of 22 and 68.

Question 3:

Jackson has 27 marbles, and his friend has 39. How many marbles do they have in total?

Question 4:

24 red apples and 18 green apples are on the table. How many apples are on the table?

Question 5: Kim adds the ones first and then the tens when

Concept Map

What we have learned

• Add numbers using place value blocks.
• Add numbers using partial sums.
• Solve model questions using partial sums.