Mental Math Subtraction

What are the strategies to calculate mental math subtraction?

The tricky strategies to calculate subtraction mentally in your head is an important part in mathematics.  Year-by-year practicing will help us to learn how to use mental math tricks or techniques in an appropriate way. Tips: practice whenever you get free time in school, at work, etc.,

There are some skills, which are used to solve the questions of subtraction easily and conveniently. Use mental math strategies to calculate subtraction to sharpen your mental maths skills.

Here are some easy examples in which mental subtraction skills are used.


Problems to calculate mental math tricks for subtraction:

1. Subtract 27 from 73.

Solution:

73 – 27

= 73 + 99 – 27 – 99

= 73 + 99 – 27 – 100 + 1

= 73 + (99 – 27) - 100 + 1

= 73 + 72 - 100 + 1

= (73 + 72) – 100 + 1

= 145 - 100 + 1

 = 45 + 1

= 46

Therefore, 73 – 27 = 46

For the solution we deduct 27 from the highest two-digit number.

               99

           -   27
               72

           +  73
             145

          -  100
               45

          +     1
                46



Now 73 is added to 72 (72 + 73 = 145)


Again from the sum 100 is deducted and then 1 is added.


72 + 73 → 145 – 100 → 45 + 1 = 46

This 46 is the subtracted result of 73 – 27


2. Subtract 93 – 67

Solution:

93 + (99 – 67) – 100 + 1

= 93 + 32 - 100 + 1

= (93 + 32) – 100 + 1

= 125 – 100 + 1

= 25 + 1

= 26

Therefore, 93 – 67 = 26


3. By backward counting subtract 5 from 19.

Solution: 

               19

            -   5
               14

19 – 5

= 19 –  I,     I,      I,      I,      I

         18,    17,   16,    15,    14

Therefore, 19 – 5 = 14

 

4. Find the difference of 53 – 29

Solution:

         53           59     →    30      →                      

                    -  29          -29             -  6
                                      30               24

Hence,          53

             –     29
                    24      

 

The above tricky strategies will help us to calculate mental subtraction to sharpen the math skills to perform easily.

Related Concepts

Mental Math Addition

Mental Math Subtraction



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3rd Grade Math Lessons

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