Percentage change

This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Sat Jun 19, 2010 1:41 pm

Percentage change

by Panaac » Sat Jun 19, 2010 1:44 pm
From 1980-1990, the population increased by 6%. From 1991-2000, it decreased by 3%. What was the overall percentage change in the population from 1980 - 2000?
A. +2.82
B. +1.86
C. +0.70
D. - 0.84
E. -1.6

The answer is A
Source: — Problem Solving |

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 » Sat Jun 19, 2010 1:54 pm
The question is asking for a percent:

Whenever the answer choices are fractions, decimals or percents and the problem contains unknowns, you can plug in your own values for the unknowns.

For percentage questions, we should plug in 100 so that the math is easier.

Let's say the population starts at 100.
It increases by 6% to 106.
Is then decreases by (.03)(106) = 3.18, so the new population is 106 - 3.18 = 102.82.

Since the population rose from 100 to 102.82, it went up 2.82%.

The correct answer is A.
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

Newbie | Next Rank: 10 Posts
Posts: 4
Joined: Sat Jun 19, 2010 1:41 pm

by Panaac » Sat Jun 19, 2010 2:00 pm
Thanks a lot!