Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

An easy way to find squares of numbers !! [#permalink]

Show Tags

16 Sep 2013, 12:33

3

This post received KUDOS

Hello. I have just discovered an interesting way to find out squares of numbers. Well, its not anything magical, but its interesting and can be helpful sometimes if you can do fast addition and subtraction.

In this method, if you know the square of 20, u can find the square of 19 & 21 by simple subtraction & addition. Yap. It works this way. If you dont know the square of any number, its not gonna work !! so, lets see an example:

20^2 = 400 ( we all know ). But what is 19^2 ? or what is 21^2 ?? finding out the square of both this numbers looks challenging to me, if I use multiplication. so, heres the trick: to find out 19^2, subtract (20+19)=39 from 400. u get 361. This is the square of 19.

Similarly, to find the square of 21, add (20+21) = 41 to 400. its 441 and it is the square of 21.

Similarly, if we know 30^2 = 900. We can easily find out, 29^2 = 900 - (30+29) = 841. and 31^2 = 900 + (30+31) = 961.. even we can stretch it to 28 and 32 as now we know the square of 29 & 31

I know its nothing super magical, but i felt very happy to figure out this relationship, which, I believe, will be very helpful sometimes..

For those of you who are interested to know how it works ( some of you might have even found it out already ):

Its simple algebra. If we know the square of the number x, we can find the square of number (x+1) and (x-1).

(x+1)^2 = x^2 + 2x + 1 = x^2 + ((x) + (x+1)) -- thats what we did for 21^2 when we assumed we know 20^2

(x-1)^2 = x^2 - 2x + 1 = x^2 - ((x) + (x-1)) -- thats what we did for 19^2 when we assumed we know 20^2

Hope it will help you sometimes..

Consider Kudos if you find it helpful. I have attached a pdf version of this post so that you can save it for later reference incase u need.

Re: An easy way to find squares of numbers !! [#permalink]

Show Tags

18 Sep 2013, 13:05

This is awesome!

I also found something recently, in questions were you are given sum of 2 numbers and have to find the greatest number when you multiple 2 numbers such as x+y = 16. The greatest number would be a square i.e., 8*8 in this case.

Please give a kudos if you found this useful.
_________________

If I look absent-minded or insane, I am just living a dream of being successful. If you still wonder why I am like this, you have no idea how success tastes like!

Re: An easy way to find squares of numbers !! [#permalink]

Show Tags

19 Sep 2013, 03:44

2

This post received KUDOS

For example- What are the values of x and y at which we have the maximum value, when x+y=16

The maximum value would be when both x and y are equal to 8.

For instance, if we take x=7 y=9, we get 63 and if we take x=1 y=15 we get 15. The closer the 2 numbers, the higher their values.

Please give a kudos if you found this useful.
_________________

If I look absent-minded or insane, I am just living a dream of being successful. If you still wonder why I am like this, you have no idea how success tastes like!

Re: An easy way to find squares of numbers !! [#permalink]

Show Tags

11 Oct 2013, 21:52

2

This post received KUDOS

Hi all,

Here is another method to find squares of ANY 2 digit number in a matter of seconds For that you would need to remember squares of numbers upto 25, which I believe most of us know.

So, here goes:

say 44^2.

check difference with the number 25 - In this case, 44-25 = 19 Then check difference with 50 - In this case, 50-44=6. square this difference, i.e - 6^2 = 36

Now, join the 2 numbers...1936..there you go, that's your answer

A slightly more difficult number this time - Say 71

Step 1 ... 71-25 = 46 Step 2 ... 71 - 50 = 21...21 squared = 441...since we have to ensure we stick to 2 digits only, carryover the hundreds digit (4), by adding it to 46..so the result from step 1, now becomes 46+4 = 50

Re: An easy way to find squares of numbers !! [#permalink]

Show Tags

11 Oct 2013, 22:37

sagiyer wrote:

Hi all,

Here is another method to find squares of ANY 2 digit number in a matter of seconds For that you would need to remember squares of numbers upto 25, which I believe most of us know.

So, here goes:

say 44^2.

check difference with the number 25 - In this case, 44-25 = 19 Then check difference with 50 - In this case, 50-44=6. square this difference, i.e - 6^2 = 36

Now, join the 2 numbers...1936..there you go, that's your answer

A slightly more difficult number this time - Say 71

Step 1 ... 71-25 = 46 Step 2 ... 71 - 50 = 21...21 squared = 441...since we have to ensure we stick to 2 digits only, carryover the hundreds digit (4), by adding it to 46..so the result from step 1, now becomes 46+4 = 50

So, your answer is 5041

Superb buddy !! Thanks :D

+1 for the method !! :D

gmatclubot

Re: An easy way to find squares of numbers !!
[#permalink]
11 Oct 2013, 22:37

Hey, guys, So, I’ve decided to run a contest in hopes of getting the word about the site out to as many applicants as possible this application season...

Whether you’re an entrepreneur, aspiring business leader, or you just think that you may want to learn more about business, the thought of getting your Masters in Business Administration...

Whether you’re an entrepreneur, aspiring business leader, or you just think that you may want to learn more about business, the thought of getting your Masters in Business Administration...