How to Find the Perfect Square of Any Number That Ends in 5

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By Fanof EHow
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A perfect square (square number) is an integer that can be written as the square of some other number. 1 squared = 1, 3 squared = 9, 12 squared = 144, etc. Did you know that there is a neat way to find the square of any number that ends in 5? This article explains an interesting method one can use to find the square of any number that has 5 as its units digit.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

paper
pen or pencil
calculator

Step 1

Pick ANY number that ends in 5. It can have two digits, three digits, four digits, etc. The important thing is that it ends in 5.
Step 2

Write the number down, write the same number below it, and underline it. Put a multiplication symbol to the left of the second number.
Step 3

Do 5*5. It’s 25. Write 25 below the line.
Step 4

Now, cover up the 5s.
Step 5

Look at the top number and add 1 to it.
Step 6

With the 5s still covered up, multiply the number obtained in step 5 by the number on the second line. Write your result to the left of the 25.
Step 7

Verify your result with a calculator. It will be correct.
Step 8

As an example, let’s do 45*45. 5*5 = 25. One more than 4 is 5 and 5*4 = 20. The answer is 2,025 and can easily be confirmed with a calculator.

Tips & Warnings

This trick works with any size number that ends in 5. On your computer, click start, click programs, drag over to accessories, drag over to calculator, and click on calculator to see for yourself. The calculator on my computer has room for 32 numbers.
Always check your answer.