NEW HERE? LEARN MORE
closeclose
Last visit was: 25 Apr 2024, 12:20 It is currently 25 Apr 2024, 12:20
Decision Tracker
My Rewards
New posts
New comers' posts

Close
GMAT Club Daily Prep
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

SQUARE of any two digit number - shortcut

User avatar
toughmat
Manager
Manager
Joined: 19 Apr 2011
Posts: 59
Own Kudos [?]: 9 [0]
Given Kudos: 2
Send PM
SQUARE of any two digit number - shortcut [#permalink] New post   01 Jun 2011, 06:05
Good tip thanks for sharing



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
bellcurve
Manager
Manager
Joined: 19 Nov 2010
Posts: 63
Own Kudos [?]: 256 [0]
Given Kudos: 9
Send PM
Re: SQUARE of any two digit number - shortcut [#permalink] New post   01 Jun 2011, 14:29
Can you please explain how you 16+2 and 9+3?
avatar
arrypotter
Intern
Intern
Joined: 11 Aug 2007
Posts: 2
Own Kudos [?]: 4 [0]
Given Kudos: 0
Send PM
Re: SQUARE of any two digit number - shortcut [#permalink] New post   01 Jun 2011, 20:54
bellcurve wrote:
Can you please explain how you 16+2 and 9+3?

Thanks mate for pointing, that is a wrong line. SOme typo there. Please exclude that line

9 | 16 + 2 |5 -- this is wrong (typo)


9 + 3 | 2 |5 - correct
User avatar
bellcurve
Manager
Manager
Joined: 19 Nov 2010
Posts: 63
Own Kudos [?]: 256 [0]
Given Kudos: 9
Send PM
Re: SQUARE of any two digit number - shortcut [#permalink] New post   02 Jun 2011, 06:02
This is a pretty cool trick. Thanks!
User avatar
AnkitK
Manager
Manager
Joined: 11 Feb 2011
Posts: 86
Own Kudos [?]: 1091 [0]
Given Kudos: 21
Send PM
Re: SQUARE of any two digit number - shortcut [#permalink] New post   02 Jun 2011, 21:35
explain it for 29 pls
User avatar
puneetj
Manager
Manager
Joined: 08 Sep 2010
Posts: 70
Own Kudos [?]: 84 [0]
Given Kudos: 18
Send PM
Re: SQUARE of any two digit number - shortcut [#permalink] New post   11 Jun 2011, 09:15
Numbers ending in 5 have a defined rule to square.
User avatar
L
IanStewart
GMAT Tutor
Joined: 24 Jun 2008
Posts: 4128
Own Kudos [?]: 9244 [1]
Given Kudos: 91
 Q51  V47
Send PM
Re: SQUARE of any two digit number - shortcut [#permalink] New post   11 Jun 2011, 09:29
1
Kudos
Expert Reply
arryputtar wrote:

29^2 how to solve this ?

Step 1: Identify the digits

29 - lets say "2" as "a" and "9" as b
So 2-> a and 9-> b

Step 2: Plug into the equation below
a^2 | 2(a*b) | b^2

instead of a -> use 2 and instead of b-> use 9

Step 3:

So by plugging in we get
2^2 | 2(2*9) | 9^2

Step 4:
solve the thing

2^2 => 4
2(2*9) => 36
9^2 => 81

4 | 36 | 81

Step 5:
this is the kewlest thing....all you need to do is carry over from right to left


4| 36 | 81 -> carry over 8 (left most digit just like addition)
4| 36 + 8 | 1 => 44 | 1
now from 44 carry over 4
4 + 4 | 4 | 1

8 | 4 |1 => 29 ^ 2 => 841


Fortunately we rarely (probably never) need to square awkward large numbers on the GMAT. If I need to find the value of 29^2, I'd take advantage of the difference of squares:

29^2 - 1 = (29 + 1)(29 -1) = (30)(28) = 840

so 29^2 = 841.

This would be a fast approach for a number ending in 9 or 1; for other numbers it would still lead to an awkward calculation.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: SQUARE of any two digit number - shortcut [#permalink]
11 Jun 2011, 09:29
Moderator:
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions