How to calculate square of a number ending in 5

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This technique will work for all numbers which end in 5.

Funda – If we remove the last digit ‘5’ from our number and are left with x, then the square will be [Product of x and x+1]25.

 

#Suppose we want to calculate 65^2.

ð  We remove 5 from our number, we are left with 6.

ð  Product of 6 and 7 is 42

ð  The square of 65 is 4225

 

#Suppose we want to calculate 195^2

ð  We remove 5 from our number, we are left with 19

ð  Product of 19 and 20 is 380

ð  The square of 195 is 38025

 

How to calculate square of a number ending in 1,9 or 4,6

This technique will work for all numbers which end at a distance of 1 unit from a multiple of 5.

Funda – Calculate the square of the nearest multiple of 5. Add or subtract (Num + Multiple of 5) from it.

 

#Suppose we want to calculate 61^2.

ð  The square of 60 is 3600

ð  The square of 61 will be 3600 + (60+61) = 3721

 

#Suppose we want to calculate 179^2

ð  The square of 180 is 32400

ð  The square of 179 is 32400 – (179+180) = 32041

 

#Suppose we want to calculate 66^2.

ð  The square of 65 is 4225

ð  The square of 66 will be 4225 + (65+66) = 4356

 

#Suppose we want to calculate 194^2

ð  The square of 195 is 38025

ð  The square of 194 is 38025 – (194+195) = 36736

 

I will continue with other methods of calculating squares in my next post.

You can buy my course on WizIQ here: Speed Calculations, Shortcuts & Tricks for CAT & Competitive Exams

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Ravi Handa holds a B. Tech and M. Tech degree in Computer Science from one of the most prestigious Engineering colleges in India - IIT Kharagpur. In the last 7 years, he has trained and coached thousands of students via his website Handa Ka Funda. He also runs a comprehensive online CAT Coaching course

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