Target Test Prep 20% Off Flash Sale is on! Code: FLASH20

Redeem
Target Test Prep
5-Day Free Trial
5-day free, full-access trial TTP

Available with Beat the GMAT members only code

MORE DETAILS
Target Test Prep
Magoosh
Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

MORE DETAILS
Magoosh

Percentage DS

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 227
Joined: Sun Apr 08, 2012 4:53 am
Thanked: 12 times
Followed by:3 members

Percentage DS

by guerrero » Sun Feb 10, 2013 10:43 pm
Price increased by M% from 1991 to 1992 and by N% from 1992 to 1993. What was the percentage increase in price from 1991 to 1993?

(1) MN=300

(2) 100M+100N+MN=4300

Please show me the Quickest approach

thanks!

OA 2
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2621
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

by Ian Stewart » Mon Feb 11, 2013 4:22 am
If you increase something by M%, you multiply it by (1 + M/100). So here, the price is multiplied by:

(1 + M/100)(1 + N/100) = 1 + M/100 + N/100 + MN/10000

So we need to find the value of this expression. Statement 1 alone isn't much help. Using Statement 2 alone, if we divide both sides by 10,000, we get:

M/100 + N/100 + MN/10000 = 0.43

So 1 + M/100 + N/100 + MN/10000 = 1.43, and the overall increase is 43%.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Feb 11, 2013 4:36 am
guerrero wrote:Price increased by M% from 1991 to 1992 and by N% from 1992 to 1993. What was the percentage increase in price from 1991 to 1993?

(1) MN=300

(2) 100M+100N+MN=4300
Let the original price = 100.
Increase from 1991 to 1992 = M/100 * 100 = M.
New price = 100+M.
Increase from 1992 to 1993 = N/100*(100+M) = N + MN/100
Total increase = increase from 1991 to 1992 + increase from 1992 to 1993 = M + N + MN/100.

Since the original price was 100, the total increase and the PERCENT increase are the same.
Thus, the question becomes:

What is the value of M + N + MN/100?

Statement 1: MN = 300.
Not sufficient to determine the value of M + N + MN/100.

Statement 2:
100M + 100N + MN = 4300
M + N + MN/100 = 43.
SUFFICIENT.

The correct answer is B.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Post new topic Post Reply
• Page 1 of 1