Subtraction of 2-Digit Numbers Mentally

Mental subtraction helps us find the difference between two numbers quickly without using paper and pencil. By understanding place value and number relationships, we can subtract 2-digit numbers in our minds easily.

What is Mental Subtraction?

Mental subtraction means solving subtraction problems in your head. Instead of writing down the numbers, you use simple strategies to find the answer quickly.

A. Subtract the tens. Then subtract the ones. (In case of subtraction without borrowing)

We check the ones digit of the subtrahend. If it is less than the ones digit in the minuend, borrowing not required. Then we follow the steps given below:

1. Find 87 - 24.

Solution:

Express 24 as the sum of the nearest ten and additional ones,

i.e., 24 = 2 tens + 4 ones = 20 + 4

Now, proceed as per the following steps:

Step I: Subtract 2 tens (20) from 87.

            87 - 20 = 67

Step II: Subtract 4 ones (4) from the result.

              67 - 4 = 63

Therefore, 87 - 24 = 63.

2. Find 54 - 32.

Solution:

Subtract Tens First

Subtract the tens and then subtract the ones.

54 − 32

Express 32 as the sum of the nearest ten and additional ones,

i.e., 32 = 3 tens + 2 ones = 30 + 2

Step I: Subtract the tens.

            54 − 30 = 24

Step II: Subtract the ones.

             24 − 2 = 22

Therefore, 54 − 32 = 22.

3. Find 87 − 45.

Solution:

Subtract Tens First

Subtract the tens and then subtract the ones.

87 − 45

Express 45 as the sum of the nearest ten and additional ones,

i.e., 45 = 4 tens + 5 ones = 40 + 5

Step I: Subtract the tens.

            87 − 40 = 47

Step II: Subtract the ones.

             47 − 5 = 42

Therefore, 87 − 45 = 42.

B. Subtract the ones. Then add the extra ones (In case of subtraction with borrowing).

If the ones digit of the subtrahend is greater than the ones digit of the minuend, borrowing required. Then we follow the steps given below.

1. Find 73 - 37.

Solution:

Express 37 as the difference of the nearest ten and additional ones.

37 = 4 tens - 3 ones = 40 - 3

Now, proceed as per the following steps:

Step I: Subtract 4 tens (40) from 73.

            73 - 40 = 33

Step II: Add 3 ones (3) to the result.

             33 + 3 = 36

Therefore, 73 - 37 = 36.

C: Use Friendly Numbers:

Round the number and adjust.

When a number is close to a multiple of 10, you can subtract the friendly number first and then adjust.

1. 72 − 29

Solution:

72 - 29

Step I: Subtract 30 instead of 29.

           72 − 30 = 42

Step II: Add back 1.

             42 + 1 = 43

Therefore, 72 − 29 = 43.

Word Problems on Mental Subtraction:

1. There were 68 birds on a tree. 23 birds flew away. How many birds remained?

Solution:

Total birds = 68

Birds flew away = 23

Birds remained = 68 − 23

Express 23 as the sum of the nearest ten and additional ones,

i.e., 23 = 2 tens + 3 ones = 20 + 3

Now, proceed as per the following steps:

Step I: Subtract 2 tens (20) from 68.

            68 - 20 = 48

Step II: Subtract 3 ones (3) from the result.

              48 - 3 = 45

Therefore, 68 − 23 = 45.

Answer: 45 birds remained on the tree.

2. A shopkeeper had 95 balloons. He sold 31 balloons. How many balloons are left?

Solution:

Total balloons = 95

Balloons sold = 31

Balloons left = 95 - 31

Step I: Subtract 30 instead of 31. (Since 31 is close to 30, subtract 30 first)

            95 - 30 = 65

Step II: Now subtract the extra 1:

             65 - 1 = 64

Therefore, 95 - 31 = 64

Answer: 64 balloons are left. 🎈 

3. Rita collected 84 stickers. She gave 22 stickers to her friend. How many stickers does she have now?

Solution:

Total stickers = 84

Stickers given to her friend = 22

Stickers left = 84 − 22

When a number (22) is close to a multiple of 10 (20), you can subtract the friendly number (2) first and then adjust.

Step I: Subtract 20 instead of 22. (Since 20 is close to 22, subtract 20 first)

            84 - 20 = 64

Step II: Now subtract the extra 2:

             64 - 2 = 62

Therefore, 84 − 22 = 62

Answer: Rita has 62 stickers now.

Note:

Mental subtraction of 2-digit numbers becomes easy when you break numbers into tens and ones. Regular practice helps students develop strong number sense and improve their mental math skills.

Tips for Mental Subtraction:

• Know your place values (tens and ones).
• Break numbers into smaller parts.
• Subtract tens before ones.
• Use friendly numbers when possible.
• Practice daily to improve speed and accuracy.

PLAY Mental Subtraction Quiz GAME:

This interactive mental subtraction game helps students improve number sense,
mental arithmetic skills, concentration, and calculation speed. Regular practice
with 2-digit subtraction problems builds confidence and strengthens foundational
math skills for Grades 2, 3, and 4.

Practice Problems on Mental Subtraction:

1. Solve Mentally

(a) 58 − 24 = _____

(b) 76 − 32 = _____

(c) 89 − 45 = _____

(d) 65 − 22 = _____

(e) 91 − 38 = _____

(f) 72 − 41 = _____

(g) 84 − 53 = _____

(h) 97 − 24 = _____

Answers

1.

(a) 34

(b) 44

(c) 44

(d) 43

(e) 53

(f) 31

(g) 31

(h) 73

Worksheet on Subtraction of 2-Digit Numbers Mentally:

Printable Worksheet PDF

About Author

Written by Priyanka Ghosh
Mathematics Educator | Founder of Math Only Math

Priyanka Ghosh has been teaching elementary and middle-school mathematics for over 12 years and specializes in creating simple, child-friendly math lessons and worksheets.

Related Pages:

• Addition of 2-Digit Numbers Mentally
• Mental Math Worksheets
• Subtraction of 2-Digit Numbers without Regrouping
• Subtraction of 2-Digit Numbers with Regrouping
• Estimation in Addition and Subtraction

3rd Grade Math Worksheets

3rd Grade Math Lessons

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