BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

How to simplyfy it?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sat Jul 16, 2011 9:58 am
Ashetty wrote: [1001^2 - 999^2] / [101^2 - 99^2]= 10 (How??)
This is a common question type on the GMAT
It requires you to factor the difference of squares in the numerator and denominator.

Aside: a^2 - b^2 = (a+b)(a-b)

[1001^2 - 999^2] / [101^2 - 99^2]
= [(1001+999)(1001-999)] / [(101+99)(101-99)]
=[(2000)(2)] / [(200)(2)]
=[4000] / [400]
= 10

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Legendary Member
Posts: 512
Joined: Mon Jun 18, 2012 11:31 pm
Thanked: 42 times
Followed by:20 members

by sana.noor » Thu May 09, 2013 5:58 am
very simple question
1001= 1000+1
999= 1000-1
101 = 100+1
99 = 100-1

now for a shortcut and to ave time
represent 1000= a....100 = b and 1= c
the above equation will be

(1000+1)^2 - (1000-1)^2/ (100+1)^2 - (100-1)^2 the final equation will be
(a+c)^2 - (a-c)^2/ (b+c)^2 - (b-c)^2---Main equation
open these equation as we know the general rule (a+b)^2 = a^2 +2ab + b^2
open the main equation and cancel out variables
in the end u will be left with ac/bc = 1000/100 = 10 answer...it took me few seconds to solve this question
Work hard in Silence, Let Success make the noise.

If you found my Post really helpful, then don't forget to click the Thank/follow me button. :)
Top
Post new topic Post Reply
• Page 1 of 1