Art of math

How to Subtract 5 from Two-Digit Numbers by Summing the Unit Number

Subtracting numbers can sometimes be tricky, especially when dealing with two-digit numbers. However, there’s a simple and effective method to subtract 5 from any two-digit number by using the concept of summing the unit number. Let’s explore this method step-by-step.

Understanding the Method

When you subtract 5 from a two-digit number, you can think of it as subtracting the unit digit of 5 (which is 5 itself) from the unit digit of the two-digit number. But instead of directly subtracting, you add a number to the unit digit of your original number.

Step-by-Step Guide

Let us take 12 – 5
add unit numbers 2 + 5 and get 7
That is a result

Another example:

Take 16 – 6
add unit numbers 6 + 6 and get 12
That is a result

Refining the Method

Actually, the process above needs a little adjustment when it comes to bigger numbers

Take 23 -5
add unit numbers 3 + 5 = 8
reduce decade number by 1 ( 2-1 = 1 number on the decade place)
add to decade 1 unit number 8 and get 18
Therefore 23 – 5 is 18

But if we take this number:

Take 28 – 5
add unit numbers 8 + 5 = 13
reduce decade number by 1 ( 2-1 = 1 number on the decade place)
add to decade unit number 1 (decade! wich means its value is 10!) number 13 and get 23
Therefore 28 – 5 = 23

Let’s look at more examples:

35 – 5 = (3-1) (5+5) = (2) (10) = 30

32 – 5 = (3-1) (2+5) = (2) (7) = 27

53 – 5 = (5-1) (3+5) = (4) (8) = 48

56 – 5 = (5-1) (6+5) = (4) (11) = 51

Why This Works

For many, subtraction as such is a problem, so here is a way to calculate differently through playing with operations.

This is especially interesting with numbers from the first ten, because then everything comes down to adding the first two digits.

Practice Examples

64 – 5
12 – 5
14 – 5
28 – 5

Conclusion

Subtracting 5 from two-digit numbers can be simplified also by subtracting 10 and then adding 5 back. This method makes mental subtraction easier and faster, especially for young learners or anyone looking to improve their math skills.

Try practicing this method with various two-digit numbers to master it quickl