Quick Square

A mathematical trick

A mathematical trick

Did you know that there is a quick way of squaring a two digit number which ends in 5?

Just multiply the first digit by that number plus one.... stick a 25 after your product and there's your answer .... simple ?


Q. What is 35 squared?
A. 3x4=12
.....now stick on the 25
...........the answer is 1225

Barry's Response - It even seems to work with three digit numbers (using the first two digit to make a two digit number) and plain old 5, using 0 as the first digit.

Oh the handy things we can do with math, games,conversions and tricks.

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Here are some other math shortcuts and tricks:

You can use these shortcuts for mental math and quick calculations.

- A two-digit number can be multiplied by 11 by adding the two digits and putting the sum in the middle. 11 x 24 is 264, for example.
- You can multiply a number by 9 by multiplying it by 10 and subtracting the original number. The answer to 9 x 7 is 70 - 7, which equals 63.
- If you wanna multiply by 5, divide a number by 2 and then add a 0 to the end. For example, 5 x 36 is 36 ÷ 2 = 18, then add a 0 to get 180.
- If you want to square a two-digit number, find the nearest multiple of 10, then calculate the difference between the number and the multiple, square this difference, and add it to the multiple squared. To find 37 squared, find the nearest multiple of 10, which is 40. Calculate 37 - 40 = -3, square -3 to get 9, and add that to 40 squared, which is 1600. Therefore, 37 squared is 1600 + 9 = 1609.
- To multiply by 25, multiply it by 100 (by adding two zeros) and then divide it by 4. To find 25 x 48, calculate 48 x 100 = 4800, then divide it by 4, which equals 1200.
- To multiply a number by 50, multiply it by 100 (by adding two zeros) and then divide the result by 2.
- A number is divisible by 3 if the sum of its digits are divisible by 3. Check with 246.
Calculate 2 + 4 + 6 = 12, which is divisible by 3, so yeah, divisible by 3.
- Same check can be used for divisible by 9.

Comments for Quick Square

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I really wonder of this Techniques
by: Rajesh

I thought it would be good and it is really good and when i am going through all the tabs so then i am keep on getting all the tips from this site.

I understood that it is very useful can understand anyone easily so there several formulas if you follow but if you follow these you will find answers with in short time.

This is very interesting site and i really like to use many times and i got solved all the problems here.

by: Anonymous

Haha, awesome! I didn't know about that trick. I wish we got taught little tricks like that in all my math classes in college.

Helpful hints
by: cangel

This is great. After all my years of teaching I was not aware of this little help. It just shows there is always something new to learn. And with sites like yours I can keep learning. I looked at the site about metric conversion and I am going to use it in my tutoring. Please keep up the good work. I have added your site to my favorites for browsing in the future. Thank you.

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