Percentages

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Sun Oct 14, 2012 1:34 pm
Followed by:1 members

Percentages

by teejaycrown » Fri Nov 02, 2012 10:23 pm
What was the % increase in the population of city k from 1980 to 1990

1. in 1970 the population of city k was 160,000
2. In 1980, the population of city k was 20 % greater than it was in 1970 and in 1990 the population of city k was 30% greater than it was in 1970

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Fri Nov 02, 2012 11:28 pm
teejaycrown wrote:What was the % increase in the population of city k from 1980 to 1990

1. in 1970 the population of city k was 160,000
2. In 1980, the population of city k was 20 % greater than it was in 1970 and in 1990 the population of city k was 30% greater than it was in 1970
(1) In 1970 the population of city k was 160,000. But this alone is NOT sufficient to find the desired percent increase in population.

(2) In 1980, the population of city k was 20 % greater than it was in 1970 and in 1990 the population of city k was 30% greater than it was in 1970.
Let us assume that population in 1970 = P.
Then in 1980 population = P + 0.20P = 1.2P
In 1990, population = P + 0.30P = 1.3P

So, percent increase from 1980 to 1990 = (1.3P - 1.2P)100/1.2P; SUFFICIENT.

The correct answer is B.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/